I think we will see as much of William & Kate post-wedding as we do currently of William. Technically not a lot is changing for him in terms of expectations for him to do Royal Duties right now as he will still be in active service with the RAF (til 2013? Have I got that right?) I think he'll do what he currently does, the big events (Trooping the Colour etc), certain events with his current charities/patronages & the other things he does with the FA, one or two "representing the Queen" like he did in Australia earlier this year & I suspect Kate will tag along to those events, not do much solo or anything. Once William is no longer actually working in the RAF, or if circumstances in his position change ie: if Charles becomes King, only then do I see any significant increase in Royal Duties & activities by either of them, maybe a small increase year on year but nothing hugely substancial til he's no longer actively serving with the RAF.
If I were them I'd crack on with having kids whilst William was still stationed in Wales with the RAF as it may give them a little more privacy, stability etc when they perhaps aren't going to be fully laden with Royal Duties & trips abroad & what have you. But that's just my own opinion there.