@VillageLife
For the country, it strikes me that becoming a full Schengen member, and part of the Eurozone, are very positive steps. From a business perspective, reducing friction (of borders/customs and money) is good. For potential travellers/tourists/digital nomads, it's also good. For potential real estate buyers from other EU countries, these two factors add to Bulgaria's credibility/appeal, and slightly simplify transactions.
My guess is that it will increase demand for Bulgarian property from within the EU, and tend to increase prices. While some folks argue that Bulgarian real estate is already too expensive, I see it as very undervalued when you strictly compare like-with-like. For example, my recent Bansko purchase was at approximately 500 euros/m2, for a finished and furnished apartment (admittedly, I do still have to do some renovation work). This is way less than you'd find in other European ski/mountain resorts. We're in Plovdiv, Bulgaria's popular and touristic 2nd city. I think you can still find a few newbuilds for 1,500 euros/m2 (ours was a just under 1,000 euros/m2), and finishing from Bulgarian Standard might cost another 500 euros/m2 (less if you're frugal). But property in Hamburg, Barcelona and Marseilles are way more than 2,000 euros/m2.
I think the record of Euro introduction is that price inflation happens as a consequence. I was living in Spain when it ditched the Peseta, and some of the price increases seemed quite dramatic (especially for lower cost items). This is probably why many Bulgarians are worried. However, Bulgaria is a bit unusual in that it has had a Euro:Leva peg for many years, and the Euro is being introduced at the same rate. Logically, there's no reason why the prices should change. i suspect there will be some minor price inflation, even so.
I'm a (relatively) wealthy foreigner, with foreign income and a Bulgarian property portfolio. It's probably going to be very positive for me. If I were a typical older Bulgarian in a small village, with a low Bulgarian pension and my small village house, it can be only be bad news (even if not outrageously so).