Short answer:
Yes. Buy it now.
All surplus firearms have risks of damage involved. But those issues can usually be repaired. And the best time to get parts (or a replacement) is when the firearms are most available on the market.
Do it now, or forget about it.
Long answer:
M1951s are a necessary addition if you want to complete a Beretta service pistol collection.
They're also a nice piece to have if you want one of the first truly viable 9mm service pistols.
And, of course, you must have one if you have a Hi-Power. It's the law.
Whether or not you want it for its service history, design evolution, or just because it's a bit different, there is one thing to keep in mind:
They won't be getting any cheaper.
Let's use the 92S as an example.
The 92S pistols have trickled into the US for decades. A little here. A little there. But never any huge numbers.
Until two years ago. Suddenly, there was a glut on the market (far more so than now) and prices were pushed down to as low as $199.
Two years ago, you could have gotten one of the better condition 92Ss (like mine) for $199.
Today, you're looking at a starting price of $339 for something in worse condition.
Next year, that'll be $399+ for worse condition, still.
In five years, if any remain for sale by the usual suspects, the price will be $500+ for ratty examples that are being scraped from the bottom of the barrel. Private sale asking prices will follow the same trend, albeit slightly suppressed.
And, of course, importable surplus firearm supplies are drying up, while the number of interested buyers is increasing. We're reaching the point where pre-machinegun service weapons have all been consumed, and there won't be anything left that can be imported (except in very small numbers and generally very poor condition - which we're already seeing with Garands, M1903s, Mosins, and the few Mausers still out there). The modern generations of collectors are also far more focused on what they want, and far more likely to impulse buy something, even if they're not sure they want it - just to be sure they don't miss out on what might be their only chance at one for a good price.
The modern generations also tend to buy spare parts for their surplus firearms before they break, which leads to parts drying up far quicker than previous generations are used to.
This triple-whammy means that import lots are sold faster and faster with every year that goes by, and everything becomes more expensive and harder to get, with increasing rapidity.
If you want, or think you might want an M1951, buy it NOW!
You can always unload it for the same price, or more, next year.