On the extreme side, playing this out through some generations in a society that does allow such modifications, a related but distinctively unique hybrid of human-machine may arise. Some call it "homo-evolutis". Something like this was explored in Elysium, Cloud Atlas, and much other science-fiction. It won't happen in an isolated way, due to the interconnectedness of the now. It will require both evolutionary and revolutionary shifts in the way R&D is done and what it is done for. Bottom line and defence will continue to drive innovation for some time, but maybe, just maybe, world peace is achieved at some time in the future (without too much death and destruction) and so happens to be a large catalyst by freeing up large amounts of the world's human and capital resources to pursue the next great evolutionary and revolutionary journeys that so unjustly go de-prioritized or non-existent on the agendas of the current world economic-political pasta of today.
I can imagine that through heavy genetic modification, physical problems such as degeneration and ageing, and even many if not most mental problems would be addressed to what some today would consider to be "miraculous" levels. Through transplantation, in-place or offsite augmentation (imagine harnessing super-computing through thought), or complete replacement, local physical diseases, imbalances, and uneven and under-development of physical and brain structures would be prevented.
Cognitive Behavioural Therapy (CBT), increased self-awareness, and better command of self-control have proven to be keystone areas affecting mental health and overall wellbeing, among more traditional chemical interpretations championed today. These areas will benefit hugely from an improving understanding of our cognitive structures that will accompany if not precede many of these other advancements.
Maybe we will be able to perform fairly accurate backups of our brain structures into a data store, to as minute as detail as possible, so as to regrow a brain using a 3D body part printer, and just about any other part for you, in case you smashed your last "physical body" on your last race with your temporary clone manifestation from 175 years ago on your personal space vehicles ;) Intelligent sentient existence will become very weird. Insert telepathy and the central global consciousness. Imagine facebook groups and whatsapp groups but with thought. The 'clone you' and the 'contiguous current you' may be very well aware that his or her (or his-her, or their) time would be limited, because he or she (or she-he, or them) that their experience would be merged onto the same base contagious current you, so perhaps that other/previous/'part'-you may not actually mind getting smashed, they may actually prefer to pause/sleep/go-offline.
Science fiction has explored this well. I liked Meronym's healing machine in Cloud Atlas. 335
I also liked the med beds from Elysium.
Others talk of nano bots running through our veins, somehow, greatly augmenting our immune systems.
Of course, almost all technology, or access to it, can be weaponized. It is my sincere hope that this does not happen, though history mostly pops that bubble fairly quickly :(
Btw, Gattaca is one of my favs!
About the specific questions:
1. What would the moral line be that parents could not cross when altering their children?
A fair and just society that allows such selective breeding would necessarily have to create fairly levelled arenas of competition for access to education, athletic competition, and the average workplace (as is explored in the movie). We can already see some of this with advanced programs at elementary and high schools in which 'gifted' children are placed. Currently there is no other way to get there than to either work really hard to improve your bets, or to have a genetic advantage - this will change in the future. It will create a collection of parents who may not be gifted, and consequently likely to be poorer, who yet desire for their children to compete with the naturally and artificially gifted. Something similar exists in the world of professional athletic competition, with their various levels of competition. Contrast the rules of professional athletic competition with professional aesthetic bodybuilding. We see that pro bodybuilding allows enhancements otherwise banned in most pro athletics. If all have equal (and fair, since this can be very expensive) access to enhancements from the start, then why does pro sports ban enhancements? Likely because not because of the fact that enhancements are expensive, though that would be one reason to level the playing field by banning them (other than ensuring safe use, etc). Enhancements are the name of the game in pro bodybuilding, and anyone and everyone who goes into it, unless if it is for 'natural' bodybuilding, is aware of that. Perhaps being 'gifted', 'natural' or otherwise, will become a prerequisite for many types of jobs of the future, as was explored in Gattaca.
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