According to whom, some anonymous source? If he actually believed Trump was trying to obstruct, then he had a duty to report it to the AG immediately, not months after the fact.
Well, Trump didn't start obstructing justice until after he was elected. But it matters little at this point...the Federal Grand Jury has already issued subpoenas that Flynn has refused to hand over. Grand Juries only issue subpoenas if there is enough to justify probable cause.
If I were a betting man, I would bet that Trump doesn't last the year. He will most likely resign, Pence will pardon him, then Pence will resign, followed by Ryan (for the coming RICO case that is ensnaring the Republican Party) who will resign as well. The line of succession is going to go to Hatch, who said he's retiring after his current term. Tillerson and Mnuchin, the next in line, have clear Russia ties, and if Trump goes down, they go down with him. Mattis, Sessions, Zinke all have questionable ties as well, and a cascading investigation will take them out. Purdue will resign; he doesn't want to be President. Ross is a part of the Russia stuff too, having accounts with criminal Cyprus banks that deal with Russia. I guess that means Alex Acosta will be the President when all is said and done...unless he quits as well because of the Trump stink (after all, Trump picked him...why?). We actually could end up with President Ben Carson only because the guy is so clueless, it stretches the bounds of reason to think he has the mental capacity to be involved in a conspiracy.