Brexit?

I assume you are UK citizen and registered at local administration as resident.
Nobody knows what will happen at Brexit as UK has decided that we are still bargaining chips. "Sufficient progress" on this subject was made in phase 1 of Brexit negotiations but is still work in progress and will depend on what UK will agree to.

I have plenty of friends so upset by the vote they already applied for Belgian nationality. As above it’s not signed off so how can anyone know, it it’s definitely been debated in depth because the EU has many citizens living in the uk and vice versa

Q - does anyone know what happens when Brexit comes into force?
A - Unfortunately no one knows, however it's unlikely that in the immediate short term anything will happen.

Whatever happens, the UK government has already publicly stated that all EU residents will be able to remain in the UK, so it's probable that EU countries will allow UK residents to remain in exchange.

Longer term, who knows.

Nearly every Brit that I know here is applying for Belgian nationality for themselves and their families. You don't have to give up your UK nationality to do that, although you will will need to have been continuously resident in the country for 5 years.

In practical terms, you need to stay in Belgium for another 2 years and then apply for citizenship. That is the ONLY way you can be certain of retaining your EU citizen's rights at the moment.

To "answer" your question, no, we don't quite know how our rights will be affected, nor can we predict how the Belgian authorities will change the treatment of British citizens in this never-been-seen-before scenario.

What is certain is that you'll be able to carry with your Belgian residency (not "EU") until you can apply for Belgian citizenship.

If you change countries in the meantime, however, you're likely to be stuck in limbo.

I wouldn't rely on any statements made by UK government which has made too many U turns, specially on immigration and their actual actions to EU citizens (who are even married to a Brit and well settled) seeking "permanent residency" has been disgusting.
The sticking point is still freedom to move to another country and return, as mentioned above.