I think it's still too early to start thinking about replacing Massa. His accident in 09 then his confidence damaging 2010 season (thanks Ferrari for the Hockenheim bull****) haven't helped him. Added to the fact that, anyone can see that, Ferrari haven't made a properly good car since 2008, showing that they haven't adapted to the new regulations yet as much as say Mclaren and Red Bull.
Anyone can see that Alonso is having to drive the wheels off of his Ferrari to get any decent results from it which is what Alonso does. Massa doesn't really thrash cars as much. I've watched him since his Sauber years and Massa isn't an all arms flying a stuff driver. If you've watched Alonso carefully, even when he drove for Renault, he moves his steering wheel like mad because he likes understeer in a car. Massa I think when he joined Ferrari, he definitely gelled better with a Schumacher designed Ferrari, oversteery. I remember the Chinese event where Massa was clearly the faster driver than Alonso. This was due to an extreme setup that him and Rob Smedley were able to work out that would work in Massa's favour. Unfortunately an extreme setup doesn't work at every track.
Alonso's presence in Ferrari isn't helping Massa one bit, and I think to be able to deal with Alonso, a driver needs to be able to adapt to a car that is made for Alonso, like Hamilton did. Both Hamilton and Alonso have similar driving styles so were able to drive just as fast as each other.
Then we need to look at Massa's 2011 season.
7th in Australia with the fastest lap.
5th at Sepang.
6th in China.
11th at Istanbul.
DNF in Spain.
DNF at Monaco.
6th in Canada after a backmarker didn't get out of the way causing Massa to drop from a potential podium finish.
5th in Valencia.
5th at Silverstone.
5th at Nurburgring where he was able to hold off against Vettel, for only a slow pit stop allowing Vettel to pass him.
6th a Hungaroring with the fastest lap.
8th at Spa after Alonso early on clumsily passed him, slowing Massa down allowing Hamilton to pass at the same time.
6th at Monza after being pitched into a spin by Webber.
9th in Singapore after getting a puncture from Hamilton.
So yes, in comparison to Alonso the results haven't been great, but this isn't all down to Massa being slower than Alonso or compared to him before his crash. The car lately really has been nothing short of off the pace.
Then we get back to the matter of Perez. This is his first season, he's had good results and is good on his tyres in a car that is easy on it's tyres. We don't know if he'll have a good 2012 or not.
In 2013 we have a HUGE change in regulations with the V6 Turbos coming back so that throws in more questions on if Perez is good and ready for Ferrari. It took Schumacher 5 years in F1 before he ended up at Ferrari. Alonso had 9 years in F1 before he went to Ferrari. Massa had 3 years before a rece drive with Ferrari, so Perez is in a similar posistion to where Massa was at the start of his career, if not almost identical. Massa was liked by Ferrari, Perez is in Ferrari's driver programe, both started their careers at Sauber, a team that apart from the BMW & Mercedes years have had ties with Ferrari.
I think that, if Ferrari can't make a good car for next year who knows if it won't be Massa saying "Bye Ferrari" looking for a better car. Perez might get promted for 2013 but I still think it's too early to say. Drivers doing well in their rookie season get this kind of attention. DiResta and Perez are in similar situations as well, with people taking about DiResta replacing Schumacher.
Lets see what Ferrari can give to their drivers for the remaning races and for 2012 because this will decide Massa's future at Ferrari.