Gulp is still a great tool for straightforward workflows. It's still being developed and maintained. It has more than 30,000 GitHub stars. There's no need to change you have a working process.
There are valid reasons to look at other build tools, but "because your current tool is 4 years old" isn't one.
There are valid reasons to look at other build tools, but "because your current tool is 4 years old" isn't one.