I'd like to see Alguersuari get a race seat and be it Caterham then because it won't be Lotus who will retain Grosjean for next year, and the HRT is a mess and probably won't be around come Melbourne 2013.
I don't know about van der Gerde, I haven't followed his career path in lower formulae.
Kovalainen had his chance in F1 and in a top team and he failed big time. At Caterham he was doing a similar job on the race day as Petrov, and usually beat him in qualifying until the last 5 or so races of the season where he was outpaced in qualifying by Petrov. It would be nice to have three Finns on the grid next year but Kovalainen just doesn't have what it takes to succeed in F1 and I don't really want to see him around just to make up the numbers.
Petrov apparently doesn't have enough roubles to get a race seat, and I won't be missing him much either. He appears to be a good bloke but pace-wise he isn't that good, despite besting Kovalainen in the latter part of the season.
Senna has his famous name and sponsorship money, but he never shined in this year's Williams which was a pretty good car. He was totally destroyed by Maldonado, who despite crashing often at least has potential.
So the answer is:
Jaime Alguersuari