Like already stated the quote was "About 10 People" keep in mind the series has changed multiple times. Oda originally planned for One Piece to be around 5-6 Years and now its past its 20th Anniversary and Oda already stated in an interview they are planning for the 30th. We also been told that the Series was mostly complete which gives us the impression the show may end with its 30th.
Alot of people stick with the crew of 10, they use Blackbeard as the reason saying there gonna fight at the end. Problem is if you count Blackbeard they are 11 and hes been openly seeking new members as seen with Kuzan.
The most popular theory is that they will end up being a crew of 13. with 4 members joining every milestone of the adventure.
Starts in EAST BLUE
Make it in the GRAND LINE
Headed into the NEW WORLD
Many comparisons have been drawn.
Zoro was first seen chained to a post, Chopper was first seen chained to a sled, and Jinbei was first seen chained in jail.
Nami was a traitor working for Arlong one of East Blue's Big Three, Robin was a traitor working for Crocodile one of the Seven Warlords. (Because of this people think Pudding) She was also an traitor who works for Big Mom one of the Four emperors.
Usopp is tech based he came with the ship Going Merry, Franky is also tech based and brought along the ship All Sunny. Although we dont think the main ship will be replaced we assume the pattern will continue.
Finally Sanji and Brook are speedsters, in suits that are known perverts. We can assume the following.
My personal favorite is the Alphabet Theory and ill also mention the Country Theory due to its popularity due to Oda practically confirming it to some degree.
AB - Brook - Austria
CD - Chopper - Canada
EF - Franky - America
IJ - Jinbei - China
KL -Luffy - Brazil
MN - Nami - Sweden
OP - (Pudding?) - India
QR - Robin - Russia
ST - Sanji - France
UV - Usopp - Africa
YZ - Zoro - Japan
With the Country Theory that leaves Germany and England