I disagree. There are plenty of foreign workers in most Norwegian tech companies I know about, but the problem still exists. Norwegian employers could be more actively recruiting abroad, and can freely do that inside the EU. I doubt that will change that much.

Say you are a young Norwegian engineer. The incentive for doing a startup is not there, because the oil industry are there and offer you high income risk-free. You may of cause make much more if you succeed with a startup, but most will not.

For a non-Norwegian, if you are going to Norway, you will also go to the places that pay best and have the most secure jobs, so to go to Norway to join or (especially) start a new new IT-business in an area that is by no means a hub for that makes less sense than joining an oil company. If you want to do a Web startup, it will probably make more sense, even for a Norwegian, to do that outside of Norway.

In Norway there has been a considerable immigration of workers the later years. There is a still a much lower mobility of the workforce in Europe than what you see in the US, much because of language.