Redmi launched the K40 series earlier this year which made it one of the cheapest flagship phone lines of the year and it looks like Redmi is not stopping there.
The Xiaomi sub-brand looks to be already working on a follow up series to the Redmi K40. Redmi general manager Lu Weibing asked users on Weibo what features they would like to see from future K50 products.

Digital Chat Station, a frequent Weibo tipster, has also dropped a few hints about the Redmi K50. These hints suggest that we could see improvements to fast charging, video and imaging, as well as screen quality in the Redmi K50 line.

It would make sense to improve the fast charging as the Redmi K40 only tops out at 33W charging for the 4520mAh battery. While 33W is not slow by any means, a lot of rival companies are already offering 50W or 65W charging so an upgrade should be in order.
The K40 series was restricted just to China but the base model of the series did make its way to certain European markets and other places as the Poco F3 so if the K50 series were to be sold outside China, they could be rebranded devices as well.