Ignore the message, the migration assistant doesn't know anything about Sage.  DATADICT stores all the table definitions.

While the data type is not deprecated yet, it is planned to be after 2019.  At that point should we convert the data type? It sounds like this may be an important table. 

Don't touch it.  If it's deprecated after 2019, then Sage has to figure it out.  And besides, upgrading SQL doesn't do diddly squat for Sage databases, just leave it at 2016 or whatever.

its at 2008 now. security can be an issue for sql that is no longer being supported....no?

Agreed, 2008 sucks, but 2012/14/16 will work fine with Sage.

Have you tried with 2019?  that was the plan. looks like the type 'image' may still be available. 

Nope, not yet.  Like I said, upgrading to 2019 isn't necessary for Sage 300 unless you have some other app that needs it.

In Sage 300 2020 Compatibility guide, it stats that it supports Microsoft SQL 2019 so you can upgrade to it without any concern if you are using Sage 300 2020. Of course you need to fully test the product before your migration as there are other factors can cause issues. DATADICT table with column TABLEDATA type 'image' is the default value and you don't need to worry about this.