Since gPlus has been integrated into the entire google experience, from gmail to blogspot, I think they have a chance against fb, but it will take a while.

Second, they have to make gPlus extremely easy to use to ensure that people will switch and stay with one product.

Third, gPlus has better video chat (multiple at a time I believe) than fb, so they have to encourage this as often as possible to keep users engaged and returning.