Does Delta always open up X, V classes?
To be able to buy a ticket in a particular fare bucket, 3 things have to happen:
1. The fare bucket must be available.
2. There must be a fare published for that fare bucket. you can check this on EF.
3. The trip you are attempting to book must fit the requirements for that published fare, such as advance purchase, minimum/maximum length of stay, Saturday night stay, etc. you can also check fare rules on EF.
Whether DL will open up lower buckets closer to departure is up to RM and is unpredictable. Barely 2 weeks out from departure, a T fare is not bad at all. I'd buy it.