Does this chainring need to be replaced? Here is a closeup of my triple:


All three rings are Shimano Ultegra and have never been changed.  They probably have at least 12000+ km on them.  I've been pretty good about changing the chain regularly although at this point I'm pretty sure that the rear cassette is in need of changing.

If you compare the middle ring with the two outer ones, it looks fairly worn (shark fin pattern).  Is it bad enough to need replacing?  If I just change the chain and rear cassette will I be entering a world of pain?

UPDATE:  Thanks for the advice so far.  I have a new cassette and chain standing by but would need to order a new middle ring since it's a bit exotic (one LBS didn't know Shimano still made Ultegra triples).  I know that there's a lot of km's on these rings (mostly on the middle one) and I'm also familiar with the "if it still skips, try changing it" philosophy, but I was hoping for a more objective answer.  Something about the wear pattern or what to look for if I put a new chain on?
Presumably with 12K+ km, and never having bought new chain rings, you have a very high cadence.  You should get a new chain every time you change your cassette, btw.  

If you are doing the work yourself, I don't see any reason to change the chain ring immediately.  Try the new cassette and chain and see how it works.  If it isn't broke, don't fix it. If it doesn't ride well after changing the first set of parts then yes, change it.

On the other hand, if you are taking it to a shop and paying for the work, it's probably worth having them put on a new chain ring while they've got it in the stand.  A good shop will test ride it and be able to tell you if it is needed before you buy.

12K is a lot of distance for the equipment, so I wouldn't hesitate to change it either way.