While I honestly think that something went on, I tend to believe that Trump knew little if anything of it.  My bet is that his people did collude with the Russians, but that they kept him in the dark.  That would explain his behavior to this point.  He is lashing out, because he feels he has been falsely accused.  Unfortunately, it is probably the most likely scenario.  If for no other reason, I just don't think Trump is smart enough to pull off that type of collusion, and he to date has shown that he has so little impulse control, that he would have let something slip by now.

All that being said, some of what he has done in reaction to this could be seen as obstruction of justice and I could see him still being impeached, not for collusion, but for trying to sway the investigation.  And in the end, wouldn't that be the kicker, he did nothing wrong to begin with, but his reactions to an investigation created an impeachable offense.