I'd say your chances of getting the upgrade 2/19 are really good from PremiumPlus. Inventory shows PN9 now, which means probably no GS are on waitlist in either coach or PP. Your chances on the return are not quite as good as outbound flight, but still not bad. PN is 0, which means GS could be on the waitlist, plus Mondays can be a little tougher than mid-week). Outbound is the redeye - so that's the more valuable upgrade IMHO. An upgrade from economy to Polaris westbound with no status would be dicey IMHO. UA oversells PremiumPlus as long as they can move overbooked passengers there into Polaris - and I'm sure that's what UA will do here if they can. An overbooked passenger in PremPlus with no upgrade request will get moved to Polaris before a coach passenger w/ an upgrade request.