Mark tips some info about MCMS vNext and it's integration with SharePoint. Goes along some of the stuff I've heard. There is one HUGE thing I am begging the folks in Redmond for as it pertains to MCMS vNext & SharePoint vNext (which I have heard and I'm assuming is a single consolidated product or a suite of products):
MCMS is built providing you the components to build a MCMS-enabled site. They give you a few OOTB placeholders and a console. You could build a site, a fully functioning MCMS site, with everything they give you. You can also tap into their event model, create your own placeholders, and extend the console. But basically, you have a TON of control in building the site... they just give you the tools. Sites no longer can be determined if they are managed by MCMS... there are ways (like the GUID links to resource gallery items, etc.), but for the most part, visually it's just another website.
SharePoint takes a completely different approach. They give you plenty of site templates & site definitions and that's essentially what you use to build your site. Yes, you can customize CSS files and the actual site definitions, but it's very complicated and incredibly time consuming to strip away the SharePoint look-and-feel and replace it with a purely customized one. Site definitions contain a mix of sealed user controls, web bots (I am still shocked these were used), and incredibly complicated CSS files (think one has well over 1000 lines of styles. Oh, and who knows that when you roll out a new service pack, if the site definitions will be over-written. In SharePoint vNext, I sure hope I see a product that provides a bunch of templates out of the box, but componentizes the rest of the pieces (navigation, search, etc) for a better developer experience.