If you have an enlarger that uses conventional 'opal glass' bulbs, it probably does make sense to have a reserve supply. Not because of the threat of any government-mandated switch to alternate technology, but rather because the major manufacturers of that technology are abandoning the market to the low-cost, high-volume shops in Asia who only do standard 60 and 100 w household bulbs. Those market pressures are far more likely to impact on you ability to find a replacement bulb in the near future than is any kind of government-enforced regulation. The last bulb I bought (a spare, from Freestyle, about two years ago) was wicked expensive!
When you ARE the niche market, you just have to get used to paying the high prices.