Say the atv2 is running 4.4 and wishes to upgrade to the newest one. Is it as easy as selecting the newest ios version in seas0npass to jailbreak?
Yes it is.
However, doing this will put you on the latest 5.3 which is TETHERED. Unless you have SHSH Blobs for 5.2 or another firmware; updating will mean a TETHERED jailbreak.
If you have been using the unit since 4.4 firmware it’s likely all of the blobs were saved automatically if you had the flash installed. If not and you updated nito during that time you would have some saved blobs.
It can be done
WinSpecToR is asking, how-to people. Meaning, this poster would like actual step-by-step instructions on the actual procedure.