I forgot that the new crossovers would be outboard. That would almost certainly rule them out for me.
Tom Thiel is planning both as options. The outboard versions are likely to be more tricked out. Internal mounting is space limited and reduces the options for big capacitors and so forth. From the pics I’ve seen, the CS3.7 has one or two 100 uF electrolytic caps and something like four 75 uF ’lytic caps. Upgrading all of these to film caps (probably Clarity CSA) will need a lot more space and it seems unlikely that you could simply replace the ELs with film without also changing the layout . . . and taking a bite out of the cabinet space. Still, Tom is planning an upgrade path for those who don’t want to go outboard.