Really? This is the first I've heard of that. Is a 1000w 5sec guy not ever going to hit 1500w with years of training?
I've gone from 1040 to 1170w over the last 7 months, and I do only training to raise FTP, no group riding, and no racing where sprints would matter so essentially I never sprint. It seemed to be rising along with all the other numbers, but now I'm a bit discouraged as to what the future holds for my sprinting.
If someone could increase their peak power by 50% in 7 years, we'd all be Cavendish, and he wouldn't be world champion. His sprint is allegedly in the 1800w range (1600w when he wasn't winning everything, and it went up a bit from there).
I got a powermeter after learning of a Cat 5, skinny guy, hit 1500w. I figured, heck, I should be able to blow that number out of the water. I've never broken 1600w, and my first efforts (mid-1400s) only went up to the mid 1500s, and I think it's more me being able to "test" better rather than me being faster.
Genetic ability caps us. That's why doping is so appealing - you can demolish that genetic cap.
You increased your power by less than 10%. That's realistic. It's possible to do that again.
I have a decent sprint. At 1200-1300w (typical for me) I'm not very fast compared to the others. But my FTP is low, a touch over 200w. Do I think I can train like mad and hit 400w FTP? That would represent a 100% increase. No way. How about a 50% gain? That's 300w.
No, the real world is 10-20%, maybe testing better will get another 10 or 20% (meaning not giving up, knowing how to pace oneself, etc).
So say you max out at 1250 watts next year. What's that mean?
It means you sprint as well as Floyd Landis in 2006. It means you have a better sprint than the guy that got 3rd at Elite (i.e. pro/am) Nationals. It means you'd beat me at most of the sprints I've done in races (and the only thing I can do is sprint). I won a field sprint leading it out from pretty far out and never breaking 1000w.
Don't get too caught up in numbers. But at the same time, if you're not totally killing it in sprints now, don't think that you'll be killing it next year.