MacBook Pro Retina 15" - 2.2 or 2.5Ghz? I'm going to purchase a new MBP (May 2015) Retina 15".

I will be using it mainly for software development and programming, Ruby, Rails, Angular JS, Git, and HTML/CSS3.

This probably gets asked a lot but my question is what would the consensus be on upgrading the processor? For £80 I don't mind going up one notch to the 2.5Ghz i7, but unless I'm doing hardcore stuff i.e. graphics/movie editing, am I just throwing money at a wall? Also will time play an effect on the speed of this? i.e. 3-4 years down the line? Will there be a noticeable difference?
If you can, your best option is to wait until October, when the new Macs come out, but if you can't, I'd go with the 2.5GHz. That extra power will be good if you intend to keep this MacBook around for a few years.