Re: the TIMELINE thread
Sentinels could have been around since 1973 while still not roaming the streets unmentioned in the main trilogy.
Trask Industries could have very well developed some sort of equipment against the mutant menace after the events of X-Men: First Class, but since at this point, mutants are still relatively unknown, and only known to governments, Sentinels are kept as some sort of "secret weapon", but not put forth in mass production. Similar to how real world United States has nukes, but we're not going around nuking everyone into Oblivion.
Then, around the timeframe of the main trilogy, mutants become more publicly known. We have a mutant terrorist attack (Liberty Island, X-Men), a near-apocalyptic event where a mutant nearly wipes out all of humanity (X2), the destruction of a dam and flooding of Alkali Lake, and finally a mutant army that commits terrorist attacks around the country, breaking out mutants out of prison, and engaging a full scale assault on the Alcatraz research facility, causing the destruction of a national landmark in the Golden Gate Bridge (X-Men: The Last Stand), and this all brings about a public reaction, and Trask Industries is the beneficiary of this, creating the Sentinel technology.
Then we have Sentinels approved by the government, mass produced, and THIS is when Sentinels begin roaming the streets.
Despite the viral marketing, I highly doubt that Sentinels are going to be roaming the streets and being publicly visible in 1973. I don't doubt that there will be a Sentinel battle in 1973, but it probably won't take place in the public eye. And even if it is, I still feel that a Sentinel program being in the Danger Room can lend credence to the idea that there was some sort of knowledge of Sentinels. Otherwise, how would Xavier know to have a Sentinel training program in the Danger Room?
You do bring up one really good point tho - the difference between comic Days Of Future Past and movie Days Of Future Past is that the comics, there is a future, and a present, and what's being changed is a period of time that is yet to happen.
In the movie version, there is a future, and a past, going back to a time earlier than events that have already happened. So this causes the "will they / won't they" questions about wiping out existing continuity. I really don't know what they are going to do, if Days Of Future Past is going to be used as an excuse to create the new timeline, to create First Class sequels free of the existing timeline, or if it's going to tie all the time periods together, or what. I personally have no idea. I don't think they would wipe out the existing continuity when they spent the entirety of X-Men: First Class leading into those events, while the events of The Wolverine confirm and further establish those events. But also, if Logan going back in time somehow establishes the past before the events of the main trilogy, then Logan going back in time essentially fulfills the apocalyptic future that they are trying to prevent in the first place. So I'm definitely curious to see what happens.