There won't be a new major Thunderbird release until about a year or so. The next major Thunderbird version will be v57. Until then, TB52 will receive security updates.

There are 64-bit Thunderbird builds for Linux, and I believe builds for Mac are 64 bit anyway. https://www.mozilla.org/en-US/thunderbird/all/

I'm not sure how that relates to TB53 (which will be released as a beta) though.

The reason I referenced TB53 is that I read somewhere that it will no longer support XP, it made no mention that it was just a beta and the next major build will be v57.

So I guess my (revised) question is will TB57 for Windows be 64bit?

Thanks

The reason I referenced TB53 is that I read somewhere that it will no longer support XP

That's correct - see the TB52 release notes. https://www.mozilla.org/en-US/thunderbird/52.0/system-requirements/

So I guess my (revised) question is will TB57 for Windows be 64bit?

There is also a statement about 64-bit Thunderbird for Windows (or the lack of) in the release notes. I really don't know whether there will be a 64-bit Thunderbird 57 for Windows. I also don't understand why this is important in the context of your question about ending Thunderbird support for Win XP.

It was related because with them stopping support for the primary 32bit OS's it frees them up to create a 64bit version of it for Windows in addition to Mac and Linux as Windows has more installations than both of the aforementioned OS's combined. That is why I asked the question.

It was related because with them stopping support for the primary 32bit OS's it frees them up to create a 64bit version of it for Windows

I'm afraid it isn't that simple. In any case, the 32-bit version will run on a 64-bit Windows.