I heard that the Military is planning to raise the Retirement age to 62. How true is that ??

If you “heard” this through unverified rumors and did not see anything in writing from the Department of Defense then it’s just hearsay. Recommendation...do your research first before presenting your questing here. If it isn’t written in a ALARACT Message, regulation, official military document, etc, it does not exist, it’s just gossip.... Good luck to you...

What is your source of information?

Haven’t heard that. There has been talk of similar actions on civilian side, so it wouldn’t surprise me.
Ups and downs: up-for a select group of people would be good (most wouldn’t physically be fit enough)-Age catches up and military life exacts a toll.
Down-in general terms, if it’s good for the government, it likely isn’t better for the servicemen. Kind of like when they change the retirement plan...
If they do lift the age, it will likely still follow to some degree the service limitations associated with ranks, meaning that longevity would remain based on profitability.