Challengers CIS: Milestone will not return in 2023, contrary to Riot's October announcement, after "thoughtful consideration" from Riot. The players from the CIS region — Russia, Kazakhstan, Belarus, Kyrgyzstan, and Armenia — are still eligible to play in the 2023 circuit under certain residency rules.
Next year's league is a sucessor to VRL CIS: Milestone, which only saw two weeks of competition before it was canceled. While according to the original statement, the plans for a new format were not ruled out, the league never resumed. The CIS region breathed a sigh of relief in late October, when Riot announced the region would be getting its circuit back.
Today's announcement again leaves CIS without competition. However, players will will have an easier time competing in EMEA. The regional rulebook no longer includes CIS as one of its league, but the five countries that would participate in the region's league are still considered within the EMEA Competitive Region.
As teams are only required to maintain three players from a league's Challenger League Territory (e.g. Spain's Challenger League Territory eclipses Spain and Andorra), this leaves the door open for players from Russia, Kazakhstan, Belarus, Kyrgyzstan, and Armenia, to participate in other Challengers Leagues.
Full details can be consulted in Riot's publicly available EMEA rulebook.