Not sure about that, it has not happened after the last few price-limitations that were issued in recent years.
If mobile internet is 50-100x more expensive beyond national borders I will simply not use it, it's a lose-lose deal (that is hard for the market to escape from, due to the large fragmentation).
The telcos make a small fortune every time a business traveller runs up thousands of Euros/Pounds/etc (often at the expense of their employer's shareholders). It's not surprising if the telcos increase everyone's fees a bit if this money is no longer coming in.
And I'm fine with that. Overall, it means previously underutilised capacity will finally be used. 99% of people were unable to use all mobile broadband when abroad, despite it being cheap and abundant. Now they can.
I read somewhere in some other coverage of this reform that the measures were expected to drain about 2% from telcos' revenues. Even if they raise their prices by 5% (which isn't given), that's (a) still a decent deal if you travel ever (but unfair that non-travellers would end up subsidising travellers) (b) quickly eaten up by the continuously falling prices of mobile plans.
"subsidising travellers"? If anything the travellers must be subsidising the non-travellers now. A couple of megabytes of data do not cost hundreds of dollars to move just because you have to route through one more network.
That's true. I believe providers exchange significant amounts of money from multilateral roaming agreements, and all that potential profit has to come from somewhere else.
What I'd like to see are providers charging a low fee for travellers to use their networks. Local users will subsidise travellers less in this case.
Personally, I welcome this step since plans are cheap as hell in most countries anyway compared to, say, the US.