Unless ECC has changed its policy since the end of January, neither the Foundation nor ECC believe that it would be wise to switch off t-addresses (or disable t 
t transfers) at this time.
Coincidentally, the Foundation engineers raised this topic on an Arborist call late last year (while I was still at ECC), and I put together a presentation that outlined what we/ECC believes needs to happen before t-addresses could be deprecated, without risking severe adverse consequences (e.g. a drastic drop in usage, delisting from most exchanges, etc.). I had planned to go through that presentation at a subsequent Arborist call but then I left ECC, and handed the presentation off to @steven-ecc and @nathan-at-least, and then ECC announced the compressed timeline for NU5, and everyone’s focus shifted to that.
I’ve asked @steven-ecc to bring the presentation along to an upcoming Arborist call, so we can go through it but, in a nutshell, we believe that there are a bunch of things that need to happen before we should consider deprecating t-addresses, including regulatory acceptance of a fully-shielded digital currency, and exchange support for shielded deposits, custody, and withdrawals (which will likely be dependent on HSM support).
@steven-ecc: Could we add this topic to the agenda for an upcoming Arborist call, and could you bring along that presentation?