I think the best way to answer would be what resolution are you playing at and what refresh rate does the monitor support? Then the next most important thing is what games are you playing or what games are coming out soon that you are looking to play.
 
If the 3070 gets you to where you get a great gaming experience then I see no reason to upgrade and would put the $382.40 into savings for the next graphics card upgrade. Then again if you are running like a 4K monitor with a fast refresh rate maybe it's worth upgrading now since the 3080 would be a card that will likely be good until the 50XX series comes out and maybe even the 60XX series before you need to upgrade.

I would say so.  You get GDDR6X ram in 10GB with the 3080.  Your existing GPU has 8GB of GDDR6 ram at a lower clock speed and processing cores.  You can't beat the price to performance of the original 3080 FTW3 Ultra.  I would do it if funds allow every day of the week and then 10 times on Sunday if possible.  The 3080 will give you more headroom for future games and is well worth the price difference to me.  Now if you were looking at the TI, then that might be a different story based on your needs, but for the 3080 non TI I would strongly recommend it if funds allow.  

Depends on what games you play and what resolution. Plus what quality you want like the settings cranked up on some select titles all the way or are you ok with turning something down to keep say 60-70 FPS on average? 1080p? NO 1440p? Kind of depends on what you are playing. Also how long do you want to wait until your next upgrade, a 3070 max settings at 1440p in games should last you at least 3-4 years until you have to start dialing things down and thinking of a replacement, a 3080 should be about 5-6  before you have to start really dialing down eye candy and start thinking of replacement. 
That extra 20-40 FPS in the most demanding games matters later down the road. right now not so much but that also depends on the game. As someone who plays a lot of the newer games and some older, playing at 1440p wanting all the eye candy maxed to me it was worth doing the step-up. Now if you asked me about the 3080 TI or 3090? I would probably tell you no get a 3080 at least on a gaming standpoint at 1440p.

Your new 3080 ftw will easily do 4k so why not/

ptd1969
Thanks for the suggestions folks.  I decided to go ahead and paid $382.40 for the step-up program to upgrade my EVGA 3070 XC3 Ultra to EVGA 3080 FTW3 Ultra.  I will only use 1440p at max setting and will not venture into 4K gaming.  I think the EVGA 3080 FTW3 Ultra will last me at least 3 years.  The warranty for this card is 3 years so I would also have a peace of mind.  I am definitely not going into the TI or 3090 category because I think that will start to be in the diminishing return territory.

A 3080 FTW3 Ultra should last you to about the 4th year when things start to slow down, by the 5-7th year is when an upgrade will be really needed as you will be in the 30 or lower to 40 maybe tops 50 FPS territory with settings turned down more and more with each new title.