I have a laptop (non DAW) with 4GB RAM that fills up fast on Windows 10.  Win 10 seems to be RAM hungry, so I would vote on at least 8 GB RAM for a Win 10 system.
 
Then, if you can swing for a SSD drive, you might not mind running that old thing for a while longer.  Assuming that you have sufficient RAM, the SSD is the single biggest performance upgrade you can add to a system
 
The SSD would not be wasted when you get a new system, you can just move it over to your new PC.  Probably get a deal on a system with only HDD, then do your own swap!

Hi, Primetime!  If you are getting along well with your current rig and money is very tight, I wouldn't worry too much about a new rig.  Definitely get 16gigs first (it's just a tad more expensive and will be usefull a LOT longer) Then save for an SSD... this will radically improve your rig.
 
The ram won't be usefull in the future but the SSD will be moveable... but these moves might be all you need for a long time.

Thanks guys, I maxed out my ram and it made quite a difference...I made a deal with the wife, she'll let me upgrade to a new machine with the income tax return...Yipppppeeeee!!!!