I just came across this article concerning ToS and Schwab's intentions. On the face of it it appears there was some debate about retaining ToS as part of the TDA/Schwab merger. As per this article, it seems they have decided to keep it, but "integrate" it into their existing platform (somehow).
https://www.investors.com/etfs-and-funds/personal-finance/thinkorswim-sunk-now-that-schwab-owns-td-ameritrade/?src=A00220&yptr=yahoo
Based on my experience as a former IT guy, it it reasonable to expect hiccups before, during and after the integration. There have already been a couple of such issues in the recent past, and knowing that ToS was itself procured by TDA (and not developed by them) should be a concern during Schwab's' integration..
Personally, I've already begun diversifying my reliance on any single platform by opening an acccount at Tradier. I still like ToS, but I'm not as infatuated with it as I once was.