Our firm will be deploying TMRs once the retention policy is in place (whenever that is). My question to this group is, if I send out a recurring meeting invite and the firm enables TMRs later, will I be able to record those recurring meetings?
It depends on the settings your administrator has set in the Teams Admin Centre
The ability to record in Teams meetings is set by the cloud recording setting in the meeting policy. If this is on in the policy applied to you, you'll be able to record and you'll see the option in the Teams Meeting.
Teams Meeting Recording Retention can be defined by two things: the first is retention policies or labels which are applied in OneDrive/SharePoint. The other is a new functionality in the Teams Admin Centre called the Recording Expiry Time (RET) which can set how long recordings are kept for by default.
The RET is a different setting that whether you can record or not. I would recommend setting up an ad-hoc meeting and see if you can see record in the meeting under (...) more options. If so, all good. If not, check with your admin if they will permit you to record before TMR RET is applied