nelly - Early waking is strongly linked to the timing of the nap, and 11am is really early for a 2.5yr old to be napping, most nap after lunch at around 12.30/1pm. I'd say in his case, this is the likely reason for his EW.
Since he's still napping for a good 2hrs, I'd say he may well still need that, so I'd be wary of cutting it out completely just yet as you may just end up making him OT. What I would do first of all is to gradually push his nap later, 15 mins per week, 30mins if you feel he can handle it, until it starts at 12.30pm at the earliest, but probably nearer to 1pm (so bear in mind this may take 4-8 weeks to achieve). I would continue to limit his nap to 2hrs (as you may find he wants to sleep longer due to being pushed further from his EW to naptime). If he goes to bed reasonably early at the moment eg 7/7.30pm, you may find that as his nap gets later, he won't be ready for bed at 7pm anymore & may need a later bedtime, perhaps nearer to 8/8.30pm. The combination of later nap and later bedtime will result in a later wakeup time. It worked for my DS & we now do (at 26 months)
up: 7am
Nap: 1-3/3.30
BT: 8/8.30pm
Much as I dislike giving up some of my evening time, for him, I find this works much better than cutting his nap short, which just makes him overtired.
If you do this but your DS continues to EW, or his BT's go crazy late i.e. post 9pm, then & only then would I cut back/cut out his nap.
HTH.xx