Russians can develop their weapons technologically, not numerically. I don't like this possibility.
They are probably planning and working on this even while they are at war.
They've already started working on guided bombs.
What Russia lacks is the industrial base to mass produce weapons, the ease of access for key weapons components that they were procuring from the West, and the general lack of skill in creating weapons systems that adequately compete with Western weapons. Virtually every weapon system they have is an inferior answer to what the West (namely the United States) produces.
What Russia has going for it is that it's not a real democracy and there are no checks and balances regarding how Putin spends Federal money. Hell, they can straight up just seize assets from their own populous if they want to do. Anyone who fights back or is a serious critic of the regime, goes to jail, or has an "unfortunate" accident that costs them their life.
Russia will have access to plenty of funds to keep the war effort going. They'll bleed their own country dry to see that reality. But make no mistake about it, Russia is not going to make any major technical innovations of weapons that will close the gap with what the West is providing Ukraine. Hell, Ukraine is inflicting a monstrous toll on the Russian Army, with the West's outdated equipment. The newest American weapons technology is 10-20 years ahead of their Russian counterparts. That's the product of one country spending $800+ billion on defense every year, while the other spends $60'ish billion. We're talking about two different worlds... And that's just a USA and Russian comparison. 30 Western countries are providing Ukraine with equipment and at least another half dozen are providing their weapons through third parties.
Russia's military tactics have not sufficiently evolved from WWII. They've tried, but when push comes to shove, they're right back to Zerg rushing their adversary and sending their citizens to the slaughter as meat shields. Meanwhile, the West's focus are devastating, pin point accurate, destructive, conventional weapons, that leave the Russians little chance. Take HIMARS for example. 16 of them (along with some M270s) essentially changed the whole conflict. The Russians literally have no answer for the range and accuracy of GMLRS, a munition that the United States are about the phase out, in favour of a longer range, higher speed variant.
There literally isn't a Russian system (MAYBE the S400) that is more capable than what the West can give the Ukrainians, when they're done clearing out their stockpiled, retired equipment.
Russia has already lost this war, they simply haven't admitted it yet. The West is happy to continue to fund it, because this is cheapest price (both in terms of money and blood) that the NATO and its allies will ever get to destroy the Russian army for a generation and damage the Russian economy for a generation.