I took a long walk around the top two sites, as proposed on the website of the Portland Baseball Group, and the Pearl District site feels forced. I liked the Rose Quarter site a lot more, but again, I still think we're a lot closer to getting an NHL team than a MLB team.
I don't think Paul Allen who owns the Trail Blazers would be very conducive to having competition in his town during the season. The NHL owner, like Phoenix, would probably want a new arena in five-to-seven years anyway. So, instead of having one team during each season (fall/winter & spring/summer) you would have two teams vying for the same people in potentially two separate arenas.
Knowing the folks in Oregon (off the cuff) - and the population of Portland being under 2 million - I'm not thinking that the spending of that elaboration would be very well received in that state.
Baseball is the better option for Portland.