Well, I am not an HVAC tech, but I keep my ear to the ground. I have never heard of any of the refrigerant types you mentioned. It seems cars and smaller A/C's are using R134, and unitary products including typical split central A/C are moving towards R 410. In any event, by 2010, just about 18 months from now, it will not be legal to manufacture new equipment using R22. You will stil be able to repair older equipment, and until I think at least 2020, service contractors will be able to purchase R22 for use in repairs. The price of R22 has already jumped up, almost double what it was a year ago, and will continue to go up as only recylced stuff, and no virgin refrigerant, will be available.
I know that just the switch up to 13 SEER 2 years ago has caused a lot of trouble, as "shade tree" HVAC techs don't have the skill and training they need to deal with those issues. This will be even worse with the change up to the new refrigerants.
If a young person was looking for a good career, an investement in a couple of years of HVAC trade school is looking good right now. Same is true for the auto repair business......"shade tree mechanics" cannot deal with today's cars. An educated, ASE certified tech will be able to make a lot of money.