TinyBooter and In-Field Update

Seeing as how SDK Version 2013 R2 (v1.0.5) August 26, 2013 uses TinyBooter, does this mean I can no longer use IFU to update boards with a previous TinyBooter version?

Will TinyBooter be changing in every new SDK?

It should not change. Only rarely

As I understand it, a TinyBooter change pretty much makes it impossible to update boards with one TinyBooter version to a different TinyBooter version using IFU. Is this assumption correct? Is GHI Firmware tied to a specific TinyBooter version (as in, can I use the latest firmware with an older TinyBooter rev)?

It is not recommended to use an older tinybooter if there is a newer version available but will 99.9% work just fine.

Since we are reaching maturity on 4.2, new SDK releases will not have a tinybooter update typically.