Will 1.0 templates and emails become unusable, or will there be some functionality built into 2.0 that will allow for them to still be used on some level? Not finding any documentation so any helpful answers would be appreciated!
Marketo has a product doc that explains what behaviors to expect when you transition from 1.0 to 2.0. I am assuming it will be very similar to what is outlined.
Many people posted articles, commentary and advice on their experiences transitioning from 1.0 to 2.0. A little research about what others have encountered and I am sure you will be in a good place comes August.
In addition to Joseph's points:
As someone who procrastinated in switching to 2.0, my advice is to just switch and then revert back if you need to.
It's too much effort with little return to try and anticipate which templates will break.
Most of our templates ended up being fine, a few needed to be adjusted by a developer.
And you'll love all the cool little improvements that 2.0 has over 1.0, that even if it is buggy you will probably push through to make it work. (just a theory!)
The best thing to do is have a Sandbox and prepare all of the 2.0 Templates you want in advance, then switch over and add the new ones.
DO NOT touch 1.0 assets at that point and you'll be just fine.
Pretty sure old 1.0 assets will continue to work but no longer be editable, nor should you.
The announcement was around the rich-text/html editor and forms 1.0 - not the email editor 1.0:
Mike Reynolds confirmed that Email Editor 1.0 is not being shut down/phased out in August: Legacy Rich Text Editor and Form Editor 1.0 are Being Deprecated August 1st