As long as Maldonado still has PDVSA 30M $ backing, he will end up somewhere, for instance Sauber. They'd certainly be interested. They wanted to hire Maldonado already for this year, but he refused and their current line-up Sutil-Gutierrez isn't particularly strong, so they'd be happy to take Pastor.
Grosjean? His buddy Boullier is at McLaren now and Grosjean is a good enough driver to attract attention of a strong team, but there is a lot of competition for the McLaren seat and it may not work out for him. Especially if Vandoorne carries on having a fabulous GP2 season.
Don't see Grosjean in Mercedes or Red Bull. Maybe a very long shot at Ferrari after both Alonso and Raikkonen have retired, but that's still a few years away by which time a new generation may have emerged and pushed RoGro aside. Force India or Williams? Maybe if Williams decides to replace Massa with someone younger and a brighter future, then why not.