They didn’t waste any time:
Going head to head with Batman vs Superman.
Not even going to be a contest. Marvel is going to kick DC’s ass.
The buzz on CA 2 is very positive; they know Avengers 2 will be a smash. This is a no brainer.
No way are the two movies going to end up head to head. One of the studios will move their opening weekend a bit.
But which? A cinematic game of chicken?
More like a Super Chicken game. 
(If the Mister Peabody movie is a success, one wonders if that is next.)
There are already rumors that Superman Vs Batman will move to the previous weekend.
The plan is that each of the Avengers characters get a trilogy (not sure about Hulk) including Black Widow (maybe combined with Hawkeye). Then it transitions into the new characters on the boil like Ant Man and Doctor Strange and the Guardians of the Galaxy. So expect a third Thor as well.
Leaper:
I’d say it depends on the progress of the productions. Two years is enough time for natural issues to cause a change in release date that neither studio will need to look like they’re afraid of the other.
I’m 99% sure a Thor 3 was already announced.
Seems you’re right.
After the way Thor 2 ended, I don’t think there could be any doubt. No way does that particular storyline get resolved in Avengers or something.
BTW Sebastian Stan signed a 9 movie deal with Marvel, which means Winter Soldier will be his third. Just an FYI…