According to a rumor circulating online, a new Nintendo Switch model could be released in the final quarter of the year. This new model will not adopt the new TegraX1+, but new custom processors Nintendo is developing with NVIDIA. The GPU will be based on the Volta architecture.
Even with new processors, however, major performance improvements and 4K support should not be expected. Production of these custom processors has yet to begin, according to information coming from Taiwan, so it seems unlikely that the model could be released before the end of 2020.
As the rumor comes from unspecified sources, we should take it with a grain of salt. The leaker, however, got a good reputation, as he correctly revealed information on mobile products before, so there may be some truth in what has been revealed today.
Source: https://wccftech.com/nintendo-switch-pro-gpu-volta-4k/