Currently my 1+ Promo from 2017 now shows the Simple Global with "Up To 5Gb of High Speed Data" on my account. If I click through on that heading, it reverts back to the 256kbps in 210 countries however. I suspect they have not revised that entry yet, or it relates to service after 5Gb is depleted. It also shows the AAA yearly free promo and T-Mobile Travel heading. It appears I also get the 4 full flight unlimited streaming sessions a year, and 1 hour per flight thereafter. These features were announced along with the recent MAX plan upgrades.
This is encouraging in that it lends credence to the rumors that ONE Plus, & ONE Plus Promo are getting the free, 5Gb high speed international roaming in 210 countries. If so, then I suspect Airalo, Flexiroam, KnowRoaming, etc. are going to take a hit on data sales. I hope they stay in business for supplemental data as needed though.
I imagine T-Mobile will get a decent amount of travelers switching from other carriers for the roaming service.