I am afraid there will be low interest among the OEMs to make competitive electric dirt bikes if they are put in a "support class" and are not allowed to compete at the top level.
I'll add my take on this which leans towards "I don't care much if there is low interest from OEMs to make electric dirtbikes". Ha. Well, I do from the sense that OEMs might spur further advancements/innovations with their R&D budgets. But really, it's not going to be motorcycle companies that make the big advancements. What more is left to advance? Primarily battery energy density and motor efficiency; Neither of which is going to come from a motorcycle company. It will come from those specific sectors and the motorcycle OEMs will buy/license it to use it. But there are other potential benefits of OEM entering electric dirtbike market. The potential for reduced pricing to the consumer. A small part of that might be from competition from other manufacturers, but the larger part would likely be economy of scale by mass production and allowance for slimmer profit per unit because they are so large and diversified unlike Stark. Another benefit I'll concede is availability. Would be nice to walk into each of the four powersports shops in our area and have a nice selection of electric dirtbikes in the brand of your choice and a place to immediatly pick up parts without mail ordering or have maintenance and repairs done. OK, OK. I'll change my answer from "I don't care much" to "it would be kind of nice". Ha.
But OEMs will follow rather than lead. I have mixed feelings on Tesla as a company, but there are parallels to be drawn between Tesla and Varg from a market-entry perspective. OEMs will likely tinker in the background behind closed doors, but will largely take a "wait and see" approach and only introduce electric dirtbikes once the data indicates there is profit to be made or, perhaps, to stop the loss of market share. KTM seems to be the most open to electric based on them having a larger variety of electric bikes on the ground. It appears that they will take the approach of introducing the small bikes to a young generation and making electric dirtbikes to coincide with that generations age/size as they grow up because they won't have ridden anything but electric. They are grooming their future buyers. Honda, Yamaha, Kawasaki, Suzuki, etc. will be even more conservative.
I can see non-motorsports parents being more open to buying an electric dirtbike for the kids to ride around the yard or campground because they don't make noise and those parents may not be up for doing/learning, or paying a shop to do, ICE maintenance. I've seen this with co-workers. We have to be realistic, though, and realize that in the big picture for motorcycle manufacturers, offroad/dirtbikes are a tiny niche market. I see OEMs focusing on, and releasing, street legal, around town electric motorcycles before getting serious about electric dirtbikes. It makes more sense from a global sales perspective.
But, in the end, I personally don't care what brand of ICE or electric dirtbike I'm riding...or pickup brand I drive, or atv brand, etc. I'm not brand loyal. I buy whichever brand fits my needs the best at the time I purchase. And even if there is only one brand to choose from, if it fits my need, then I'll buy it and be happy with it. And I don't buy into the notion of caring about what brand everyone else is riding (including buddies, racers, or friends on the internet). And don't much care if anyone else notices or cares what brand I'm riding. The Varg is on the horizon and it will fit my use case great and once I take delivery of that and Stark sticks around, there really isn't any impact whether or not the OEMs are interested. I'll ride the Varg for the use cases it will cover and my ICE bikes/ATVs for the ones the Varg will not. When things advance more in the battery energy density front, which is really the only advancement that will benefit my trail riding use cases, then I'll look at what brands are available that fits my needs and change to that. Be that a newer generation of Varg, or one from the big OEMs, or some new startup that hasn't even been formed yet.