If it does use a smaller fan, then yeah they could increase the battery, but then we are talking about more than significant gains in battery life. I think both will be kept the same, and the modest spec bump will allow an almost docked handheld profile.
As for Bowser's Statement, a refreshed OG Switch isn't new hardware if you think about it. In any case, I feel this is gonna be a 2DS/New 3DS scenario, but in the same year. Randomly dropped Press Release for the Lite model, more formal Direct announcement for the refresh. I'm thinking September Direct after the Lite/Links Awakening come out, Late October/Early November Release.