Personally I would be a bit nervous. I know on big budget films there can be as many as 16 people working on post... and thats for a 3 month turn around.
It boils down to the talent of the team, efficiency of the equipment being used, and the lives of the people involved. If everyone is as free as a bird then the time might not be as big of a problem. If there is a TON of design work to be done, and not many sfx that can be tagged with stock library, then the talent plays a factor.
You mentioned foley being a big deal in the film, if you are lumping foley into the SFX (which some people do and some people dont... I think it has to do if you work in the US or if you work in Canada) and your team is handling it all, then its gonna be work and a lot of overtime. If foley is being handled somewhere else, then maybe just dialog and sfx isnt that bad. But what about BG's? (same US and Canada concept applies)
A full element mix can/usually take 2-3 hours per 10 min depending on the material to be mixed. (If you are faster, then 'friggin awesome) With breaks and no problems and using a usual work day for reference, I would say it could take around 3-5 days for final verification on the print. 'Leaving about 4 weeks to edit a 2 hour film... yeah I still stand by my first statement.
But good luck to you and your team! It may seem crazy for now, but it usually all works out in the end.
Curtis
C3sound.com