Yes, the congregation monthly donation arrangement will cover over any inbalance in publishers' donations for a while, since the burden is spread across all.
So for example, you might have only say, 10-20 out of a congregation of 100 giving a substantial amount each week, with maybe a similar number putting in change and the rest, nothing. But the 10-20 giving the most will mask the lack of contribution from the rest when taken in aggregate as a monthly donation to the Org. For a while at least.
But over time, if the number of those willing to donate larger sums continues to fall, and assuming those who currently donate most are middle-aged to elderly, long-time Witnesses who have limited outgoings and sufficient finances to be able to make larger donations, such ones will continue dying off and not being replaced by ones with very stable finances (even younger ones with a half-decent income are more subject to changes in their fortunes, due to family issues, job market, inflation or recession, etc, so less likely to routinely make substantial donations), the shortfall will eventually be noticeable even at a congregation level.
At that point, even the "congregational monthly donation" arrangement will be insufficient for the Org, so they'll have to think of something else by then.
I suspect it will be tied to individual donation arrangements via online using the JW org accounts, which they are gradually trying to get everyone tied into. You already have one of these if you are an elder, MS or fulltime servant, or someone who has volunteered to do any construction work or other projects through your local Bethel. Probably won't be long before they expect everyone to use a JW login account. Then they can monitor individual financial contributions and give targeted "encouragement" to anyone not thought to be giving enough (even though scripturally, Christians are not supposed to do that!)