You can fly IFR in a RV, without autopilit, if you follow all applicable FAR's and common sense. However +1 on autopilot and competent currency for any single pilot IFR Ops. You can fly without autopilot, but if you get distracted with a task, get into an unusual attitude pointed down, speed will build quickly in a RV, faster than a C-172. Are you Instrument rated pilot now? If yes how much instrument time (on IFR flight plan and/or IMC) a year do you fly? Do you fly with or without autopilot now?
I hand flew my RV-4 IMC with no autopilot, but 100% of my attention was flying. Fishing for charts was not easy. The NICE thing about hand flying IFR with RV's is they handle nice, they are precise in their control, do what you want not. However being short coupled in turbulence, they yaw or fishtail. It is controllable by hand and instruments, to be sure if you are competently current in your RV for IFR Ops. I am not sure how autopilots keep up to the RV's in turbulence, never used autopilot in an RV.
My RV-4 had VOR/LOC/GS/MB and VFR GPS (for situational awareness). Approach approved GPS were N/A 20 years ago. My typical IFR/IMC time was popping up for IFR climbs to VFR on-top or IFR let downs from VFR "over the top". This is way safer than trying to circle up/down in a hole. Also departing IFR to VFR due to morning fog, popping out into the sun at 500 or 1000 feet AGL was great. IFR capability is handy landing at busy Class-B or Class-C airport, even when in VFR WX. Filing IFR to busy airports in congested airspace makes arrival straight forward, verses a convoluted VFR arrival you never flew. 90% of my RV-4 flying was VFR. All the hassle of equipping and keeping your RV current for IFR Ops, in retrospect, was not worth it. However it added safety and options. On the other hand, many VFR EFIS panels today have IFR NAV equivalent ability (moving map, approach plate overlay). Not legal to file IFR, at least you have this information for reference for VFR flight. Not saying fly IMC/IFR in violation of any FAR, but it does add situational awareness, along with terrain avoidance. My current RV-7 project will be "Deluxe VFR Cross Country", with advanced EFIS and autopilot. If I want to fly IMC I'll do it at work or rent/borrow an airplane.
An autopilot, even for VFR is great, it adds equivalent MPH block speed on cross country, by holding TRACK precisely (verses small track wondering when hand flying). I talk to many RV builders/VFR pilots, and they look at their autopilot as saving their tail if they inadvertently fly into IMC. I'd agree that is a selling point, but as a CFI/II, prefer pilots practice their instrument skills as well. Even commercial pilots instrument skills suffer by using the autopilot too much. Now, today there are so many quality single and two axis autopilots to chose from, at reasonable price, with installation kits for RV's, it's a much easier decision and choice to make building today. Many EFIS panels have autopilot option add-ons, as well as the standalone autopilot brands, TruTrak or EZ-pilot. All good stuff.