Standard argument from ignorance ... "hey look you don't know what you don't know so we might invent long enough ladders to be able to climb to the next galaxy". Well in fact you are wrong, we are fast advancing to knowing a fair bit or what can be known. I know it may sound familiar. What is well know is the cost of pushing the boundary of knowledge is growing fairly consistently. So in a century we will need half the worlds resources to learn 1% more where as now we need 10% of the worlds knowledge and a century ago we needed .1% of the worlds knowledge.
Ultimately it might not be possible to cross into another galaxy much like it might not be possible to travel back in time to make two planets occupy the same spot with no ill effect ... but you don't know, there are still people working in garages.