Portland would be a great fit as it keeps the A's in the west and would open up a tremendous rivalry with the dooooche canoes in Seattle. Portland has clamored for a team for years and while I was once upon a time a pie-eyed dreamer who thought it would happen one day, I'm pretty skeptical.
1) I don't know where in the hell you'd put a stadium. The Blazers and Timbers play in the heart of downtown with light rail service stopping by both stadiums several times a day. The stadiums are compact and blend in well with the surrounding downtown area. Not sure where a baseball stadium would fit. There are some options on the table, but each of them has plenty of drawbacks.
2) I honestly don't see the city of Portland supporting a team for 81 games. I mean...there will absolutely be some diehards who go to every game and I'd definitely be in for season tickets with a group, but Portland isn't a huge city and there's a lot of dorky people who couldn't tell you the difference between an outfielder and an infielder. The Blazers are a big draw, but that team is part of the fabric of the city. Likewise, the Ducks are always sold out, but that's a handful of games and winning draws in all sorts of folks. Asking this city to back a transplanted team for 81 games might be tough, unless, of course, the As are still the best team in baseball.
Hope it happens. Would be a better fit than Charlotte for the key reason I cited above about keeping the As in the west. But getting this city to agree on a stadium will be the major hurdle.