Disney is acting as fast with Tiana as they did with Maelstrom converting to Frozen, which is to say they are taking their time. Tiana just gives the appearance of going faster because we can see visible work. Remember, it's not opening until Fall 2024.
Disney does a lot of things slow, but when they reskin or do updates to rides, things tend to be a little faster. Star Tours 2.0, Test Track 2.0 (8 months for both), Soarin Around The World (flick of a switch after they tested it overnight), Festival of the Lion King relocation (5 month show hiatus). Frozen took the longest out of these more recent things at 21 months. Tiana will have taken around that same 21 month if it opens in October.
If we think that the Frozen/Tiana ride conversion timeline is something that would be similar with Dinosaur (there's no real reason why it should be much different), then IF the ride were to close in January 2024 (that's a very big if), then it would probably be announced for a 2025 Fall opening. If they wait until later into 2024 or even early 2025 to close the ride, then you'r looking at late 2026 at late 2026 at the earliest with an opening possibly falling into 2027 if it maps similarly to how these other high profile conversions have taken (or in Tiana's case, is planned to take).