I have a modest Dash holding from when Dash was a lot cheaper than it is now with the current price spike. I hold other coins too. What I'd like to ask is this -
Is Dash immune from blockchain bloat and, if it isn't, whether this will be an issue at some point in the future?
Dash has been founded in 2014, is three years old and currently has 2.6 GB blockchain size
Blockchain bloat is not and will not be a problem for Dash.
The Masternode network will continue to carry the full blockchain and getting rewarded for it, while the Dash Evolution update (end 2017) will enable Lightweight wallets / SPV wallets for endusers / merchants.
Here's my concern and you have highlighted it very well in your second paragraph. Dash will do doubt be used more as the number of payment providers increases. Mass adoption, if it happens, is bound to affect capacity available in each block. How can you say so definitely that blockchain bloat won't be a problem in the future?
By saying that lightweight wallets in an indirect way are a possible solution to blockchain bloat suggests that it will be a problem if Dash is widely adopted on an international scale. Lightweight wallets are off the blockchain and as such could be viewed as being prone to becoming centralized with all the perils associated with centralization.
By the way, I was stimulated to post after seeing the recent Bitcoin Core vs Bitcoin Unlimited debate which was mentioned in this thread the post before my original. Basically, I'm trying to work out which coins to concentrate on.