No, superconductors have a specific current above which they stop superconducting so you will want to stay away from that limit. This particular superconductor has been presented with a very low Ic (150 mA in the original paper0 which would not make it particularly useful in such applications but future iterations (assuming it is all true) may improve on that (they should otherwise we have the equivalent of a superconducting straw).
Yes, it would be upending just about everything because the race would be on to improve on that. Think of it this way: once you show that something is possible at all there will be substantial funding available to improve on it. As long as you can't show that it is possible at all you're on your own. So if it works and that 150 mA is the limit then you can expect a ton of effort to be expended to improve on that and I fully expect those improvements not to take decades to show up. The more interesting question is if it really is that low of a limit what the reason is for that and I don't recall seeing any explanation so far.
On another note: a superconductor that can only do 150 mA / cm^2 seems intuitively strange, as though that figure is somehow off, it's a gigantic cross section for such a small current. It is very well possible that this is somehow an error in the reporting or an actual measurement on a thin sample with small cross section. So there are many explanations possible and only one of those is a true limit of the material.
The current hypothesis is that most likely whatever they made is not a pure sample of the material which actually superconducts - this is expected, since when you make YBCO superconductors you also tend to get low yields (i.e. ~20%) that actually superconduct.
So it could be the whole sample, or it could one micron-sized link of grains of whatever the "real" material is running through the sample.
No, superconductors have a specific current above which they stop superconducting so you will want to stay away from that limit. This particular superconductor has been presented with a very low Ic (150 mA in the original paper0 which would not make it particularly useful in such applications but future iterations (assuming it is all true) may improve on that (they should otherwise we have the equivalent of a superconducting straw).