The "t" sound is coming back to often after being away for 300 years. When I was younger, I don't think anyone used the pronunciation of often-with-the-t. I noticed it a few years ago and researched it to try and understand what was happening. I wondered at first if my pronunciation ofen was more of a New England pronunciation, gradually vanishing as it was exposed to a national tendency to keep the t. This did not turn out to be true.
Pronouncing the "t" is an overcorrection, used by frequent readers who suddenly worried about 20 years ago whether they had been saying it wrongly all their lives. They hadn't. Ofen was the only correct pronunciation until recently. But the reemergence of the "t" has been explosive, and at least 25% of the population uses it now. I will hazard a guess that it is people who have more exposure to the archaic word oft that are leading the change.