LS was trying to simplify how they called the different sizes / series. The series sizes are the first number after MT, the next 2 numbers are the engine HP. Examples: MT1 is subcompact size (MT1 22, MT1 25). MT2 is small compact size (MT2 25, MT2 30, MT2 35, etc..). Again, all the same size frame / tires, but different loader capabilities, PTO power, etc. MT3 series is medium compact (MT3 45, MT3 50).
Similar to how John Deere lists their tractors, 1 series, 2 series, 3 series, etc.
They will eventually get ALL of their tractors under the MT designation.
To answer your question, yes the XG3025 was replaced by the MT225E. The only difference was a beefier frame at the engine mounts, and an electronic throttle control. The loader had minor changes, (and a new number), but they are interchangeable. No other changes were made to the tractor. I purchased one of the last XG3025 that were made before the change over in name. I have the new loader and heavier frame, but not the electronic throttle.
LS now has the new MT225 S listed on their website and the specs / sizes are the same as the XJ 2025. I am assuming it is the so called replacement or renaming of the XJ2025.
Hope this has helped you understand and I was able to help.