Migration from 3 to 4 will certainly be a pain but then you're gonna love it. I love new cards, utility classes, better out of the box support for mobile browsers.
But beware of breaking changes between alphas, there are quite a few.
But beware of breaking changes between alphas, there are quite a few.
Speaking of Foundation, I dunno, it depends on one's needs.
Some people say Bootstrap is too big but I appreciate its vast collection of components. Especially when you do CMS / control panel kind of apps and you need to make them quick, Bootstrap is a saviour.
Also, aesthetically I like those rounded form controls, buttons and cards. Plus it takes only a few lines of scss to make bootstrap look branded, add custom fonts and most people won't even guess it's Bootstrap.
So if you've been considering Foundation this could be a window for Foundation to pick up some marketshare.