The US will probably be a superpower forever and always. There is no denying the power of the mighty United States. This is threatened by other nations, especially the BRICS nations, however the future is uncertain. Probably the United States will maintain superpower status for at least the next few generations.
Let's start with Russia. Russia is NOT the Soviet Union. You can forget Putin's dream because if Russia went to war with the US, the States would win. China's not much different. It's military and economic growth is impressive, but the US is too far ahead for China to catch up before it hits a wall. No one else is anywhere near the US, so I think we're good.
I do not think that the United States has lost its status as a superpower in the world. I think the gaps are filling in, however. I think that the US needs to do a lot of soul searching to get back to where they once were. I still think that the US is a superpower.