Permanent Fitness / FTP Improvements from Dedicated Cycling Block?

Question for the forum, and perhaps something that ought to be (I don’t think I’ve seen it previously) covered on the Podcast.

I’m a time constrained triathlete with only 7-10 training hours per week (for all three sports). I currently use TR 3ish times a week, typically two one hour and one 90 minute sweet spot workouts. My FTP hovers around 320, with weight at 180 lbs (81.6 kg), or a little under 4 W/kg, which I think is passable for a triathlete, but not out of this world.

My question is whether there would be a benefit to a dedicated bike training block (potentially over the winter), and whether the benefits derived could provide a permanent “baseline” FTP improvement? I seem to have plateaued on the bike, and with limited training time I’d need to reduce my running / swimming volume in order increase my time on the bike. If I were to dedicate a training block to the bike over the winter, and then went back to my typical 3 workouts a week after, would any of the improvement be permanent?

Really appreciate any thoughts or insight!

Anecdotally, I’ve seen a lot of benefit from doing periodized training blocks. I never dropped the other 2 sports completely, but shifted focus to prioritize one over the others. During those times I was able to much improve at whatever I was focusing on, while the other two sports either maintained or suffered minimal decreases. Once I got back on a more well-rounded schedule, I quickly got back up to pace with everything else and felt the improvements of what I had been focusing on stuck around.