learn something new or not?

i'm having a complex today. i was reading a business book, to keep myself fresh, and there's a tip in there that says, "be sure to stay in your nitch area. don't offer multiple services to try to please everyone. just stick with what you know to be successful." obviously, in not so many words, but that's my take on the chapter.

so, the thing i'm having trouble with is this: as a graphic designer it's very important that i stay "in the now" with design trends, tools, software, periodicals, etc. it's a lot of work! but when this crazy internet thing hit a while back, everything became digital. graphic designers turned into website designers, postcards turned into email campaigns, etc. now there's, what i feel, a whole sister-world out there that's related to graphic design. but there are so many uniue components to the field, you know? worrying about usability and search engine optimization, etc.

the complex i have is coming... if graphic designers have to learn how to do web work to stay afloat and to be able to stay "in the now" is that betraying the laws of good business? is it considered going outside of your specialty just to make a convenient one-stop-shop for clients? or are the two fields so closely related that it's not really another realm, just another form of graphic design? i'm very curious to know what people think about this.

personally, my opinion falls somewhere in between. i think it's great to be able to learn something and come to know it well enough that you can offer it to clients. it creates a package deal, and again, the aforementioned convenience. however, sometimes i think i'd rather do just graphic design than design/program websites... that maybe those things should be left for the solely website designers. but why should it be left for them, if i can do it well too? maybe now i need to stop thinking of myself as a graphic designer who can do website design, and instead think of myself someone who is of both professions... see how complex this is?