A recent AMA held by the devs of Overwatch has officially confirmed what many people perhaps anticipated: When the sequel goes live on October 4th, it will be “a replacement for the current live service.”
Readers will recall that what would happen to the original Overwatch when the sequel was announced at BlizzCon 2019 was pretty murky: Jeff Kaplan said during a panel at that same event that the team would not be “leaving the live service behind,” and he stated in interviews that the goal was to change how people view sequels, expanding the scope of the game without abandoning players who were already invested in the original. Of course, the design of the game has clearly changed in the last couple of years, as have the people leading it, so now we have clear confirmation about the fate of the original shooter.
On the subject of players invested in the first game, another answer confirms that existing currencies will carry over, while lootboxes will not, though the contents of those lootboxes will be included in the transition.
Other answers in the AMA discuss the differences between maps for Escort and maps for the new Push mode, some brief nods to updates made to Symmetra and Moira as well as support heroes in general, and what the sequel’s launch means for new players. A Redditor has fully assembled all of the answers from the AMA for your perusal.