Is there much point in this thread. The only person that will know this is yourself. You say you have had these forums for years and you are earning from them. So really you already know your forums potential as you have had them and been earning from them for a while. All you have to do is try and monetize them further more so that you can try and increase your earnings further and happy days. All the best.
I would keep working on it, 5000 uniques a day is a great established base for growth. If you can get that 5000 uniques a day to 50000 uniques a day I can assure you, you will be able to live off that website then use its presence to promote any other sites you wish to create easily.
I have a combo website/forum that gets around 10,000 unique visitors & 30,000 pageviews/day and has over 14,000 active (or semi-active) members. The site generates an average of $6k-$7k/month, but generated over $8k in December. Earnings were originally only from Adsense and Kontera, but now that I've instituted a Premium Membership area, that has become the biggest earner. I guess that if you monetize right, you can make a living.. Keep building that traffic and you can make a GOOD living..
Just making conversation and hoping to get some new ideas. That is what these forums are all about aren't they?