It's never too late to take lessons. However, with 40+ years of self taught playing, you have some deeply ingrained habits and techniques. You need to find a teacher who will be able to accurately assess your current skill level and be able to develop a method for you to use that as a basis for moving forward.
A good teacher who is able to do that can really be an asset to your playing. One who insists that you go to square one and start from scratch may not be all that useful.
Having said that.... you didn't state your current music reading level if any, and if that even matters. Most teachers I have been familiar with insist on reading the music. And they teach from that perspective. Obviously, you've been playing like I play.... from hearing the music and playing it by ear. I took 7 years of piano lessons and was fortunate to have had a teacher who not only taught the reading of the music, but theory as well as allowing for and acceptance of playing by ear.
The other option is to simply continue to play the keyboard more often and work on learning new piano parts in songs you like. The more you play, the better you will become. I don't know what your playing/practice schedule looks like, but are you currently spending an hour a day playing and practicing scales and other finger exercises and learning new, more difficult pieces? If not... there's your answer. All the teacher is going to do, essentially, is to make you practice more. If you want to read, you can pick up a computer program that can help with that..... but it comes down to the amount of time you are willing to put in at the keyboard simply playing.
My 7 years of piano lessons came to a very abrupt halt when I went to my teacher's house for my weekly lesson. She opened the music book to the song she had assigned and asked me to play it. I launched into it and when I finished she said.... "That was nice. Now... would you mind playing what's actually written on the page?" I fumbled through the piece. She asked me how much time I had spent practicing the piano that past week. I said maybe 30 minutes total.... I fudged, since it was less than that. Then she asked how much time I spent playing the guitar.... I said an hour a day and I fudged that one on the short side..... I spent several hours a day playing along with the radio and my 45-rpm records. She told me to go home and practice the guitar and stop wasting my mom's money and her time. Mom was mad for a while. So I continued on as a self taught musician.
What do you think you would gain by having a teacher? Or, would you be satisfied to simply play better and could you accomplish that with more one on one time at the keyboard on your own?