Before we go any further, the answer in short is don't leave Google Plus if you're a business, and don't be afraid to start a new profile either. I'll explain why below, but in case you don't know the backstory, here it is.
Google Plus has struggled in numbers when compared to Facebook, there's no question. When the chief evangelist for the product, Vic Gundotra, resigned last April, the death cries for the social network began, from TechCrunch to Forbes. There were a few bloggers who saw this as more of a transformation in the making than a visit to the place where Google Buzz was sent to live in exile, but they were the outliers. Then came the changes: Hangouts became a separate app, Picasa became a separate app, and the final nail was driven—the decoupling of Gmail accounts from the G+ profile. The final gasp.
Don't Go Anywhere
Understand, G+ was never meant to be a Facebook replacement at its core. One of the architects of the platform, Chris Messina, recently railed against what it had become and Google's failure to improve it. He said that when it was being developed, Google Plus was known internally as Google Me. The idea was to be a hub of Google users where you could decide what information to share with who. Which sounds a lot more brilliant than what it became.
For a Facebook-marketing-like campaign you probably don't want to waste your time on Google Plus at this point, or at least not prioritize it. But even if no one is there 'socializing', there's still a lot of information flowing through there: it is Google after all. You still want to share quality content there and interact as best you can.
What does Google do, primarily? They rank websites algorithmically so when you type something in the search field you find what you're looking for. The more information they can gather, the better. The more you share with Google, the more they drive sales your way. And even if G+ ceases to be as we now know it, Google isn't going anywhere. It's a smart play to keep your profile active for the time being or until they pull the plug, which wouldn't likely be soon.
Google Me
As for what should happen, I think Messina's remarks unveiled what Google Plus should have probably been, Google Me. You set up your profile and set your privacy levels, and share content through your profile. Any time you're "googled", the relevant information and links show based on the person's relationship to you. At that point the information gathering portion is done, including your "likes".
Whether it's Google Plus 2.0 or Google Me, or something completely different, Google will develop something new. They always do. A Google Plus profile that's complete and regularly fed automatically translates to a good Google profile, and when you get down to people finding you in a search Facebook won't help you as much as Google.
Socialty is a full-service social media marketing and social recruiting agency in Chicago. We create content, websites, blog posts, email marketing and strategic marketing plans for small and medium size businesses. Our social recruiting team helps you attract talented candidates via social media outlets. Socialty connects you to your audience and potential employees. We'll keep you social while you carry on with your business. Keep Social and Carry On!