The most credible rumor talked about two upcoming Switch revisions. One of them being a smaller, cheaper version, so naturally the new chip would be used for more battery life on a revision that already aims to improve the portable aspect of the Switch. Likely launches at $250 because $200 would be too drastic under the current circumstances where Switch sales are going at a great pace.
The other one being a modest upgrade, not something like the PS4 Pro was to the PS4. This SKU can be expected to replace the current Switch which will be phased out. The MSRP remains the same, but the new SKU offers better battery life and improves games that use dynamic resolution (hardly visible to the average gamer, if at all), but there won't be a general performance boost to all games. It's more likely that the increased capabilities of the chip merely result in less usage of the fan inside the console when it is docked.