That could be a possibility, considering Intel's past, but if other motherboard makers follow MSI's example in pricing, it's probably a message to AMD and users, that 3-4-5 years of firmware support can't come cheap and definitely not for free.
A manufacturer building a motherboard for Intel today, knows that after Rocket Lake they don't have to support any new series of CPUs. With AMD I bet many manufacturers where not happy seeing AMD making the favor to AM4 owners to announce support for even the 5000 series on old motherboards with 300 series chipsets. Manufacturers, when they where putting a price tag on 300 series motherboards, probably they where not expecting to keep making firmwares for those motherboards in 2022. If they knew it, those motherboards could have been more expensive.
Motherboard manufacturers have to keep selling new motherboards every year to support themselves. With someone buying an AM5 today and not having to buy again a new motherboard for the next 5-6 years, motherboard makers will make it sure to get higher profit margin from that buyer in that period of 5-6 years. So, (as an example with random numbers) if they have to sell two motherboards, one Intel and one AMD that costs them to make $100, they will sell the Intel motherboard for $150, expecting the buyer to swap motherboard at least once in those 5-6 years and the AMD motherboard $200, expecting that the buyer will probably not swap motherboard for the same period of 5-6 years. Doing that, they can expect a profit of $100 from both buyers in the period of those 5-6 years.
if this is the case, we can expect AM5 motherboard pricing to keep declining years after year, the closer we get to AM5's end of line.