I doubt that you will get an official answer from those who are official involved with T5 but since I do know a little, I can answer in general your question
MGT is base on the orginial (or known as Classic Traveller: CT) with updates, and some new things added.
Several of the new things added are taken direct from or in the same context of T5 material.
T5 is new and different. There are many new things added.
Some are brand new, some are a different way to do the things, and some are clarifications based on all editions of Traveller.
T5 (if Marc goes that way) will be its own game but will allow usage into any other Traveller version.
MGT being based on the core of what Traveller is and is the current and hottest Traveller out there, will of course be able to use T5 material quite easily.
Also, as Mongoose's Traveller License develops, I am sure that you will see new things for Traveller. As a matter of fact if you glance around you will already see some new things out based on MGT core rules.
If this does not answer your question, please ask again, with more details and I will see what I can answer.
Please note: I have been told that
DonM and other T5 officials don't like when I tell things like the above, but don't let that stop you from trying to learn more about it.
Dave Chase