It doesn't invalidate the greater southern path, which put the possible crash site in a much broader area - about 1,200km long - than the region from which the suspected 'recorder pings' were coming.
Its very bad if we don't have any pinger data and we just have the arcs
The Bluefin searched 850 square km. That search took about a month (there were a few interruptions due to equipment problems, which will also occur in any subsequent search).
Assume the flight ended right on on the final arc, which we believe has a resolution of approx 10km "wide." That is 1200 x 10 = 12000 square km. Thats at least 12 months.
If we assume MH370 could have glided say 100km beyond the final arc, thats 120000 square km or perhaps 10 years.
Then you have to allow for increased technical and logistic difficulties as the search goes further south. The initial search was relatively close to Australia and in relatively calm waters. It will get far harder as you search further south.
Who is going to fund this?
Sure you can use multiple AUVs, but we are still looking at years.
I fear we are going to need another source of information to narrow the area down significantly.