Russia probably can't compete with the whole world arming one country. either Russia will run out of money or Ukraine out of people. I'm betting on Russia out of money.
Especially with how conservative Ukraine is being with it's troops and it's counter attacks. There have been a number of reports of their tactics being based around attriting the Russians while keeping their own troops alive.
While west is arming Ukraine, they are doing it half-assed. Usually sending them old weapons, in batches and slowly. Why wait months for sending them ATACMS?