There are currently 396 skills you can buy from the market. The average rank of these skills is just under 4.3.

To max all of these skills will require 433,152,000 skillpoints.

At 2000 sp/hr this would take you 216,576 hours = 9,024 days = 24 years and 9 months.

Undoubtedly if you planned on training all skills then, especially with neural remaps, you could maintain a higher average sp/hr than that but it is still a long time. 3000 sp/hr would reduce it to 16.5 years.

However the salient point was made earlier, that CCP have consistently added more skills increasing the time requirement by longer than the game has been around. Assuming this continues it will be impossible to get them all to level 5.

Edit: Additional Information - To just have all skills regardless of level.

In order to have all skills to at least level 1 takes significantly less sp than all skills to level 5, as obviously there are numerous high rank skills that are not pre-requisites of any others.

To do this would take around 80.6 mill sp although this only includes the rank 3 learning skills to level 1 which would be less time efficient overall than bringing them up to level 4.

80 mill sp at an average of 2,000 sp/hr would take around 4.5 years to complete.

You would end up with:

91 skills at level 5 with an average rank of 3.13. There would be one rank 14 skill, one rank 12 and 4 rank 8s

46 skills at level 4 with an average rank of 3.48

8 skills at level 3 with an average rank of 1.625

2 skills at level 2 with an average rank of 3

The remaining 249 skills would be at level 1

So doing this really wouldn't provide any kind of rounded character at all. You would be okay with T1 frigates and cruisers I guess but pretty poor with everything else.