It's likely that 710 AM will end up doing better than 97.3 when the stations split. 710 will be an okay station regardless of the local product because people will find the Mariner games. Instant cume, as KOMO would attest, with little matter of the kind of programming around the games.
FM will suffer, in my view, because the audience isn't there for the lame product KIRO keeps pumping out. The news product will continue to dwindle with more layoffs. I wouldn't doubt that they'd can the news alltogether and put a talk show in morning drive. Why not? It would save money. Anyone who seriously wants news doesn't need KIRO to get it. Traffic can only save them so long, and there are NO compelling news anchors or reporters to keep listeners coming back. Don't forget KUOW has been doing news for years, and although it's novel to people inside the Eastlake building, FM news is nothing new.
I'd bet by this time next year 710 will pull a larger share than 97.3, and Bonneville will wish it hadn't destroyed KBSG.