I noticed when LOS was first announced, they had a different date for when it was supposed to be set, later it was changed to be 1047. I also remember them adding in the references to the Cronqvist family later in the dev cycle, as I think the text on the scrolls was the only reference in game to this....also the mention of Rinalodo Gandolfi was probably added in at the end of the development of the game. This leads me to believe that a conscious effort was actually made to try an connect the game to the existing lore at some point late in the dev cycle.
The change frm the orignal date, to 1047, meant it was closer to the events of Lament of Innocence, set in 1094, and kept the "25-odd" year gap between generations that the rest of the games follow (therefore Leon from LOI would be Gabriels grandson.)
At the end of LOS, there is no real event that suggests Gabriel changes to Dracula straight away...only the 1999 (if it is 1999) epilogue shows this. Anthing could happen in those years in between!
When the DLC was announced, I saw some mention of Gabriel needing to retrieve an item from Carmilla in the castle, and REALLY hoped it would end up being the CRIMSON STONE from LOI. If it was, then it fitted in perfectly with Mathius's plot in LOI, as Mathius would simply be Gabriel who had found out about his past, taken his old Cronqvist name, and simply not aged in the past 53 years! But, alas it didn't show any of that...though it didn't contradict it either.
If this rumor about the trailer is true...then if this
new Simon Belmont is Garbriel's son...the he could simply be an ancestor of our 1600 Simon Belmont. This 1081 version of Simon Belmont would also be the perfect age to be Leon Belmont's father.
So, nothig is actually contradicted..and all Castlevania games can exist in one timeline!
Disclaimer: a lot of the above was done from memory of my understanding of the original Castlevania timelines. If there are any factual errors, let me know!!!
EDIT: forgot about the whole Bernhardt castle plot points that connect Lords of Shadow with Lament of Innocnce...another hint that there is supposed to be some connection!