Al's being a little terse here. Regarding "discontinued processor", translate this as meaning (a) not available from Intel and (b) only available in the secondary marketplace (which Intel has no purview over). Regarding "BGA package", this means that, in most cases, the processor is soldered down on the motherboard and not easily or reliably replaceable. In some cases, the processor is soldered to a small daughter card that *is* replaceable, but the daughter card design will be proprietary to the laptop/tablet manufacturer and typically only available as a used part through the recycled components marketplace.
In general, you should consider laptops and tablets as not being upgradeable and, IMHO, attempting to do so is a waste of time and money.