Hello friends we know that everyone have different moto behind playing this game like someone have to complete their pokedex someone have other vision but but suppose the player which start playing this game in 2018 so it is possible to Catch legendary like raikou, entei ,sucine lugia?
No, not right at this moment.
Their turn in the Raid rotation has been and gone.
There is speculation they will most likely return at some stage during 2018 but when exactly is anyone’s guess.
Hopefully, they won’t come at the same time. That would be pure chaos in (my) local raid group. “I come if it’s Articuno.” “And I come if it’s Groudon.” “Oh, it’s Suicune? Then nobody would come.”
But legendary event 2018 give the chances to capture them.i think so.
What legendary event 2018 
As long as they return outside of raids, I’m all for it.
I think they will release them again at some point for new players and younger players who did not play when the earlier legendaries were available, but who knows if trading is implemented some day?