Although OPSEK is currently a proposal and creating a space station requires a huge amount of budget.
Russia may extend it's hand to ESA if there is any possibility, there are discussions happened like what after 2025?
Cooperation with Europe and the US
In 2008, Russian plans for maintaining presence in the low-Earth orbit
in general and the creation of a successor to the ISS in particular,
had been met enthusiastically in Europe. As ESA had little hope to
match the US effort to return to the Moon at the beginning of the 21st
century, preserving a destination in low-Earth orbit seemed critical
for the political support of the manned space flight on the continent.
In June 2009, Simonetta Di Pippo, ESA director of human space flight,
told the editor of RussianSpaceWeb.com that she shared the Russian
vision of the future space station as a platform for deep space
missions. "I have continuous consultations with officials in Russia.
We meet every month, month and a half, and now we are going to start
jointly, the study how to proceed beyond 2025, Di Pippo said, ..."and
we have a common idea that we would like to preserve presence in the
lower orbit. We are studying different scenarios, whether we need
permanent presence or, maybe, a human-tended capability, and we can
end up with a totally different solution in the end, but I don’t
believe we can leave Earth orbit."
Di Pippo also said that although current NASA plans for return to the
Moon reserved no essential role for the station, it could change in
the future. "Even on the NASA side, they have too many different
developments (associated with the Earth orbit), including commercial
involvement, which they can not immediately give up," Di Pippo said.
By the end of 2010, all partners in the ISS project were expected to
agree on an extension of the ISS lifespan from 2015 to 2020 or even
2025. Once end of life for the ISS had been decided, active planning for post-ISS manned space flight could begin in Russia, Europe and
possibly the US.
There is also an open option for Russia from it's partners from BRICS.
China possess own space station program with ambitious objective lift
first module of new fully modular station in years 2020-2022. One of
the countries possibly interested in cooperation with Russia could be
India. ISRO still have not announced any news about their plans for
creating independent space station and their astronauts training
center in Bangalore is at the beginning of the development.
Cooperation with Russia, experienced with manned missions, could be
vital for Indian manned space program and change its position from
launch service provider to country with manned space program and share
in space station. One from Arab countries, like Saudi Arabia (with
signed agreement for further cooperation with Roscosmos on June 2015)
could also participate in program; in this way it could easily put its
space program forward and get independent access to space.
Although only china and india has remarkable presence in outer space and they have their own space ambitions and projects to complete.