Is it good for me to buy MacBook Pro 2015? Would it be added to the vintage or obsolete models anytime soon

There is a slight difference in the 13" & 15" models. However, I believe the 13" model was sold until some time in late 2016 which means that I would expect the 2015 laptops to go Vintage fairly soon since Apple usually tends to make their computers Vintage after about 5 years on average (there are some exceptions). For reference, the 2014 model is about to go "Obsolete" in about a week.

Since the 2015 laptops can run macOS 12.x Monterey, you should still have a supported OS which continues to receive security updates for another 2.5 years. The Mac can still be usable after that, but you may begin to find out that some things may no longer be supported. I'm not an Apple developer, but I would imagine that Apple may not support app submissions from developers running an outdated OS (or it becomes more risky).

Keep in mind when purchasing a used Mac, that you need to be very careful the Mac does not have a firmware lock (aka firmware password), and make sure the Mac is not still being managed & controlled by the previous owner (usually will receive message after a clean install if Mac is connected to the network, and other times will get random macOS notifications). There is nothing you can do to remove a firmware lock or management system since you will most likely not be able to provide valid proof of purchase since you are not the original owner. Purchasing a used Mac directly from Apple is safest (or perhaps from an authorized reseller, but I would still be careful with the latter).

FYI, when buying a used computer you should always perform a clean install of the OS by first erasing the drive before reinstalling the OS. Besides making sure you have a clean & stable OS with no nasty surprises left over from the previous owner, this process will usually alert you to a firmware lock and whether a Mac is still being managed by a previous owner.

AceDeRap Said:

"Is it advisable to buy MacBook 2015 now? Will it be good for programming? Will it be added to the list of vintage or obsolete soon?"

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I'd Just Upgrade:

Updates typically go for 7 years or so (and sometimes longer, depending on dependability by consumers). So, soon enough, things will not be available. M1 is the new processor, which 2020 and after Macs have. So, if anything is of concern there, it may be incompatibility. So, getting a 2019 model is more ideal, if you want to get a somewhat "older model".