Which contributed modules are being moved into Drupal 8 core?
Modules brought into core
Entirely:

Breakpoint
CacheTags
Content Translation
Email (simple field, HTML5 validation only)
Entity API
Entity Reference
Entity view modes
File Entity
Link (simple field, HTML5 validation only)
Phone (simple field, HTML5 validation only)
Picture
Quick Edit
Transliteration
UUID
Views
RESTWS (Renamed to REST module)

Partially:

Admin Views (reworked)
CKEditor
CTools
Date (all except recurring dates)
Display Suite (view modes)
Internationalization
Migrate
Views Bulk Operations (reworked)

Removed

Blog (moved to contrib)
Dashboard (moved to contrib as Homebox)
Open ID
Overlay (fundamentally reworked to not provide an &quot;overlay&quot;)
PHP Filter (moved to contrib)
Poll (moved to contrib)
Profile (Use Profile2 now)
Translation (replaced by Entity Translation)
Trigger (use Rules now)
Signature (functionality provided by User moved to contrib)
XML-RPC (moved to contrib)

Modules fundamentally changed by Drupal 8:
Deprecated (you won't need these anymore)

Admin
Administration Language
Bean
Boxes
Caption Filter
Computed Field
Ctools exportables
Fallback Language Negotiation
Field Hidden
Fieldable Panels Panes
Float Filter
Hidden Field Widgets
History
IMCE
Localization update
Localized Drupal Distribution
Menu Block
Menu Trails
Module Filter
Node Reference
Placeholder
Profile2
RSS permissions
Services
String overrides
Strongarm
Token
Transliteration
User Picture Field
User Reference
Vertical Tabs
Wysiwyg * (the module and everything related to it)

Reduced (these will have less work to do)

Backup and Migrate
Context
Custom Breadcrumbs
Features
Feeds
Menu Breadcrumb
Service Links
Rules
Views * (every module related to views)