I think it's an issue everyone on this forum get concerned. Here's how I think about the issue.
I think no one on this forum can give you a definite answer. I would also think, manufactures themselves may not be able to predict how long they will manufacture their last film. Many are reducing their product line up because of the demand and thus prolonging the availability of film as whole.
Assuming your intent is to stay in photography, I think the choice is fairly clear. Say you want an SLR of any kind, digital, 35mm, or 120 (MF), you have certain expenditures. You pay for the body, lens, and supplies, and thus you have an annual expense. That's ultimately what your concern is, isn't it? You don't want to end up with an equipment with its associated expense and no use. Say, you spent X amount of dollars or whatever your local currency, and no way to use it because supplies have dried up.
IF you are going to be in digital realm, you have this upgrade thing going because the technology is constantly evolving and improving. So you have X amount of dollars spent per certain period. I have to say this value is rather high.... and fairly short lived. When it comes to film gear, the advancement is basically over. You can get a top level gear for basically nothing. I have a set of newly acquired Mamiya RB with all the lens I could possibly want and I spent about $1500 I think. I intend to use it for few years at minimum. I think it's a safe bet 120 film will be around for few years, possibly quite a bit longer. So my annual expense falls....
I fully predict, at certain point in time in future, film and whatever needed will be so expensive and rare it will be impractical. But, because of this annualized expense being relatively low, I have no issue buying whatever I want and need and ENJOY IT NOW and for foreseeable future. Also, my interest may change and future situation may change. I don't try to predict the future for more than few years at a time for something like this. And for the next few years, it looks pretty stable.
Also consider, hobby expenses are ultimately a waste, if you want to really analyze it. You get enjoyment out of it and that's your ROI. (Return on investment) So I say don't worry, buy it, and get the maximum enjoyment out of it.
I don't know your age, financial situation, interest, future plans, or anything, so what I said may or may not relate to you. But this is how I think about the issue.
And I'm heading out with my newly acquired (pair of) Horizon Perfekt, a panoramic film camera I just bought new. I spent about $500 for two. (they were on sale)
PS. I fully expect 120 film to be readily available at reasonable cost for 5 years. I also expect it'll be available in one form or another for 10 years at obtainable costs. I think, 15 to 20 year span may be questionable. How's that for a bold prediction?