I think Interlagos will not return for, at least, several years. The hosting fee was been paid by Emerson Fittipaldi but he had massive losses due to low attendance. Imo, the "they'll be working on the track to improve the facilities" used for saying it's not on this year's calendar is nothing but an excuse. Afterall, isn't Uncle Bernie's circus visiting the circuit this year?
Hope Canadian public money doesn't go to paying WEC's fee. A very boring circuit comprised of awful slow-high-kerbed chicanes and a hairpin. You don't built prototype cars, with decent amount of downforce, to be climbing slow corners' kerbs. LMP1/2s needs tracks like Silverstone and Spa(lot's of high speed corners)
Don't see why there would be a event on Mexico as the only reason F1 will be back there is because of Mexican driver(s) being there in the last few years. Don't see any appeal for WEC on Mexico.
Motorsport(specially endurance racing) is not super popular in Italy. F1 has been losing massive amount of viewers there(see graph bellow), so I don't see a WEC race happening.
I read in the begining of the year that the first couple of 2015 GPs were under 1 million viewers on Italy.
In Germany, the huge drops regarding F1 tv ratings are similar(year on year decrease since 2009). I'm far from sure Nurburgring is a safe event, btw. We'll have to wait but I suspect grandstands will be empty...