We know folding wings are a nonevent as far as risk is concerned, but no B777 orders were ever received for taht option, which was formally offered IIRC.
B777X and 787-10X will have different markets, so it's no surprise they'd offer both. Moreover, with the final completion on both B787 and B747-8 they have the capacity to do them both. B737MAX will not be a huge stretch either.
I am possessed of no solid information on these views which are based from avidly following the recent developments, and studying all I can find about Boeing development history. After all, derivatives are easier, and both the 777 and 787 are very modern FBW aircraft so have decent technology on which to base the new derivatives.
The combination of British Airways and Emirates, both seemingly avid 777X buyers, make that one seem to be a foregone conclusion anyway.