1) Do we know if it will be more widespread? Although the stronger stuff is also illegal in the Netherlands, it's very easy to find and I don't think the Netherlands have more drug addicts then another country (no source for this, just my opinion how I know the country).
2) Is it a problem if it's more widespread? Some stronger stuff can be used responsibly (for example MDMA). Just like only a small portion of alcohol users have alcohol problems. You also got stronger stuff like heroin which is very addictive, but then there's still common sense. Whether it's legal or illegal, I can get it very easily where I live. Yet, I don't take it because I know it's not good for me.