2013 27" iMac i7 to 2016 27" iMac i7 Trade up?

So I bought a 2013 iMac with an i7 processor, 32GB of RAM and a 3TB fusion drive. I have a client who wants to buy my computer, which is in pristine condition, for $2500, and I would buy a new i7 iMac with Retina Display, 32GM RAM, upgraded video card and 1TB SSD drive for just over $4000. Should I go for it? I'm wondering if I should wait for the announcement in March from Apple...maybe there is an update to the iMac. Opinions and feedback welcome!

Mark