One thing I was wondering about was porting TC to other architectures; x64 would be the low-hanging fruit, ARM would make a tremendous amount of Good Sense considering its recent surge in popularity and availability in low-end hardware.
Of course, that leads to the next issue: more architectures means that the current way of having extensions created by the community would inevitably mean that there would be inequalities between architectures; it's not too hard to imagine that extensions for ARM would be considerably outnumbered by those for x86. Which leads to the conclusion that if multiple architectures are adopted, a move to a script-based compilation procedure would be the way to go. That way, users don't contribute binaries, but compilation scripts. As an added bonus, this would go a long way toward prevent hostile submissions. (What's preventing users from adding a root kit or keystroke logger to their submission? I am certain that the vast majority of submissions are absolutely clean, but it only takes one rogue to spoil everything for everyone.) I would recommend against the NIH syndrome and take an existing system from one of the source-based distros. GoboLinux (while not exclusively source-based) has a very nice system with Compile, and many of the scripts (recipes) are only two lines. Other options would be SourceMage, CRUX, and of course Gentoo.
I hasten to add that I don't think that TC should become entirely source-based; rather, a hybrid, where the user can either build an extension from source or download it as a binary, but in both cases the extension would be created from the same script; the binary would have just been pre-compiled.